What is a Christian tape measure ? It is a measuring device that Christian's use to measure others. It could present in a way like saying I am right and others are wrong. Or that others are better than oneself.
Jesus said whatever measure we use to gage, evaluate, correct etc. others will be used to measure ourselves too.
When we say others are preaching the false gospel, we have to make sure we are not preaching a false gospel too. What is a false gospel ? A false gospel is a gospel that Jesus never taught.
Did anybody ask about the standard measure or true measure? I believe God has it or Jesus got it. Let us submit ourselves to Jesus standard.