I can think of several cases of that happening. In particular I remember a contributor who said he was a young farmer who wanted to try to understand the arguments for veganism. I suspect he was genuine and was attempting to examine his conscience. Anyway, he received lots of responses and eventually left with absolutely no acrimony.
What sometime bugs me is the occasional once only poster who asks a question (often about needing support) receives lots of well thought out concerned replies but then immediately disappears without even the courtesy of a little thank-you. I suspect that some of them are not just lacking manners but are trolls attempting to get a few vegans agitated.
If that is my greatest forum moan then I guess things must be being done about right.
Roger.