I think it's a bit like "compassion overload". Someone new to the discussion is more likely to take posters who start off with "I have always believed in Apollo, but I have one, small nagging question, could anyone help me with it?" at face value. However, soon one starts to see that this is often not an honest post, but a ploy. Eventually, the occasional new poster who simply *does* have an honest question gets snapped at. When you are dealing with mostly wolves in sheeps' clothing, the occasional genuine sheep triggers a suspicious response.
Unfortunately, I've seen several cases where a new poster started off like this, people agreed to give him/her a chance and assume s/he was legitimate, only to show later on that s/he was simply using the "just asking questions" gambit.