They've noticed that there are secret "in the closet" apostates in the congregation. Remember that study article for December 2013? Warnings against those who speculate. It's a crack down and rise in paranoia. I'm gonna hate it when this study comes out, I'll have to be more careful with what I say.
I was also thinking, Paul lived in a time when christianity was still fresh, where there were men who knew the correct way to undsrstand the scriptures, from a biblical view. There were men who taught controversial doctrines but the apostles were still alive. Anyway, the point is that 2,000 years later, there are many religions who claim to be "the truth", believe that they teach the correct thing based on their interpretation of the scriptures. How are we suppose to figure out who's right and wrong? Without examining doctrines, scriptures, and looking at other points of view, it's all one sided. One teaching could be weak and false but you wouldn't know cause it's the only explanation given. No critical thinking.