This is a good thread, although the original poster doesn't get the points made by others, but that is fine. Every man must be persuaded in his own mind, for starters, therefore if one can not see, another person point doesn't mean it is right our wrong, but justification is truly by faith, and if we adhere to the faith of Christ we will see clearly upon all things.
Your question was, "Who is the imposter Jews"? Well to know that answer, we must also first know who the real Jews are, and who the imposter Jews are, who they imitate, and who they are not.
Once these questions are answered, one will have full understanding, if they are answered by the spirit of God, and not a fleshly perspective.
How does the bible say the real Jews are?
1Therefore thou art inexcusable, O man, whosoever thou art that judgest: for wherein thou judgest another, thou condemnest thyself; for thou that judgest doest the same things.
2But we are sure that the judgment of God is according to truth against them which commit such things.
3And thinkest thou this, O man, that judgest them which do such things, and doest the same, that thou shalt escape the judgment of God?
We have to be careful as we make judgment according to our fleshly understanding. It is not in a title, that makes one a servant of God, Child of God, Sons of God, or a Jew. If you walk after the flesh you are truly none of these things mentioned.
If you are called a Jew, Christian, or anything else under the sun, pertaining to only who you convey (speak/open show) yourself to be, then all these practices are vain, and should be counted as dung. If you walk as a man with only fleshly understanding serving the flesh, the same judgment you judge one with is the same judgment you get back, because the same things one judge another in, the one doing the judging is not worthy to judge, because they commit sin also. So much for mans court system.
Gods judgment is the only pure judgment that we should be judged with. If you are not transformed by the renewing of your mind, being reconciled now, called a son of God now through the spirit, being heirs of God, and joint heirs with Christ, then Gods judgment has not yet judged you righteous. If one is not yet counted or judged by God as righteous, then one should not judge others, but let judgment condemn themselves to loss there own wickedness, to become a son of God, patterned after the first begotten.
4Or despisest thou the riches of his goodness and forbearance and longsuffering; not knowing that the goodness of God leadeth thee to repentance?
5But after thy hardness and impenitent heart treasurest up unto thyself wrath against the day of wrath and revelation of the righteous judgment of God; 6Who will render to every man according to his deeds:
Everyone will be judged according to his deeds, either if it is of God, or some other nature.
7To them who by patient continuance in well doing seek for glory and honour and immortality, eternal life:
This is the real Jew, which are also those that are lead by the spirit.
8But unto them that are contentious, and do not obey the truth, but obey unrighteousness, indignation and wrath,
9Tribulation and anguish, upon every soul of man that doeth evil, of the Jew first, and also of the Gentile;
If one follows after this, no matter what you call ones self, or what one judges someone else to be, this same person will also be judged according to there deeds.
10But glory, honour, and peace, to every man that worketh good, to the Jew first, and also to the Gentile:
11For there is no respect of persons with God.
God has no respect of persons, meaning he is not partial to any particular group according to the flesh, or to what one will call there self. Honor and peace is judge upon those that do good. Doing good, is submitting to God in all points. If you submit to God in all points, then titles don 't matter, but you give power to the title either in obedience to God, or disobedience to him. If you are disobedient to God, whom are you obedient to?
12For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law;
This simply means that no matter where you are in your understanding, right is right and wrong is wrong, and one shall be judge accordingly. If you sin continually, not dieing to the nature of the flesh while you live, you are without the law of God, which is the law of the spirit, one shall be judge accordingly. If you know the law of the spirit, which is submitting to God, by faith, believing the word of God to be true, then to not follow is sin within the law, and one will be judge by the law.
13(For not the hearers of the law are just before God, but the doers of the law shall be justified.
The doer is justified, because he has faith in God, through Christ Jesus that lives within him. This is the real Jew, christian, and sons of God, anything else is an imposter as the post asked the question.
14For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves:
The Gentiles at one point didn't have the knowledge of the law, and what was commanded by God, but once they understood who God was, even without complete instruction, or details of what they should and shouldn't do, committed to doing what was given to them by faith. In doing so, they followed the law of the spirit, which is faith and commitment to God. This kind of person, when truth is revealed, they are able to receive it, and make the changes need to cut off the fleshly nature.
When you are a person trying to save face, and not suffer loss, then you don't abide by the spirit of God, but by your own nature, doing what the fleshly nature (you) want to do. This kind of person will continue in all those things instituted by man, be it religion, ritual, customs (man made holiday), and anything such like because they are not willing to suffer loss for Christ, counting all those things as dung.
A person that is willing to suffer loss of all things, through the knowledge, wisdom, and understanding from God, they abide by the law of the spirit, which is obedience to God in all points.
15Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another
16In the day when God shall judge the secrets of men by Jesus Christ according to my gospel. 17Behold, thou art called a Jew, and restest in the law, and makest thy boast of God,
18And knowest his will, and approvest the things that are more excellent, being instructed out of the law;
19And art confident that thou thyself art a guide of the blind, a light of them which are in darkness,
20An instructor of the foolish, a teacher of babes, which hast the form of knowledge and of the truth in the law.
21Thou therefore which teachest another, teachest thou not thyself? thou that preachest a man should not steal, dost thou steal?
22Thou that sayest a man should not commit adultery, dost thou commit adultery? thou that abhorrest idols, dost thou commit sacrilege?
23Thou that makest thy boast of the law, through breaking the law dishonourest thou God?
Be careful and not let your own teachings, and judgment come upon your own head do to the fact that you may not be righteous yourself.
24For the name of God is blasphemed among the Gentiles through you, as it is written.
If one himself is living wickedly, but preach righteousness, your ways will not be hid, and it will be revealed to all. Those that see this will despise your teachings, even in what you preach about God, they will blaspheme because of your wicked ways.
25For circumcision verily profiteth, if thou keep the law: but if thou be a breaker of the law, thy circumcision is made uncircumcision.
What is the law that we shall keep that will make us free from the law? Romans 8:2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
If you obey the law of the spirit your circumcision is profitable. But if you don't keep the law of the spirit, which is obedience, then your circumcision is not counted, it is as filthy rages, to the Jew first, then to everyone else, because judgment is at the Church first. If you didn't keep the law of the spirit, then there is another law that you will received, being law less.
1 Timothy 1:8-10 8But we know that the law is good, if a man use it lawfully;
9Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers,
10For whoremongers, for them that defile themselves with mankind, for menstealers, for liars, for perjured persons, and if there be any other thing that is contrary to sound doctrine;
If you fit this kind of person, you are an imposter, no matter what you call yourself, to the Jew first, and to everyone else also. Most don't understand that there are two laws mention in the bible, and that is the law of the spirit (obedience to Gods word) and the law of sin and death (reserved for the disobedient), which was also given by Moses to the children of Israel letting them no that if the don't keep the commandments (law of the spirit), they will be punished by the law (law of sin and death).
The way to escape the law or to be not under the law, is not do the things that will get you placed under the law. If you are now renewed to be obedient to the law of the spirit, then your are not under the law of sin and death, therefore making all things lawful for you, because you don't serve the fleshly nature any longer in sin.
Back to Romans 2
26Therefore if the uncircumcision keep the righteousness of the law, shall not his uncircumcision be counted for circumcision?
What is the righteousness of the law? It is the law of the spirit, which is obedience by faith. If you do that, then no matter if your flesh is uncircumcised, your heart is circumcised, and the uncircumcision of your flesh will be counted as circumcision, because you are now obedient to the law of the spirit.
27And shall not uncircumcision which is by nature, if it fulfil the law, judge thee, who by the letter and circumcision dost transgress the law?
We are all born in the flesh being uncircumcised by nature, both male and female. Keep in mind the female is not instructed to cut the foreskin of her flesh, being the token of the circumcision, so how would a women fulfill that token if that was so important? No matter, and moving forward, if you keep the law of the spirit being obedient, you have fulfilled the law of the spirit each day that you continue to submit to God. When you submit to God, bringing the body subject to the law of the spirit, your flesh is circumcised, because you have cut the sinful nature (foreskin) away from your heart, therefore the physical body is also circumcised. Isn't this also physical not to sin, for when you bring the deeds of your body subject to God, that is also spiritual and physical, that is real circumsision. That is the real circumcision, but to many people count the token of the circumcision (cutting of the foreskin) as the circumcision, but there hearts remain uncircumcised, making the cutting of the foreskin not counted by God. For if you cut the flesh, and your heart is not right, you are not circumcised.
28For he is not a Jew, which is one outwardly; neither is that circumcision, which is outward in the flesh:
Your outward show of whom you are in any custom does not make you a Jew. The real Jew is one that is a Jew inwardly, being brought subject to the law of the spirit everyday, being made free from the law of sin and death. These are the real Jews, and any other, by any other way is an imposter.
29But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.