Several years ago, a friend turned up at my house who I hadn't seen for some time. Initially pleased to see him, I got concerned when it turned out he had had a breakdown and had then found god. As in found == full blown fundamentalist, as it's written in the bible, speaking in tongues etc.
It got worse as he spent the evening telling me that, I was still a dear friend of his. However he could see demons standing behind me and it was his duty to save me.
It was a truly horrible and scary evening, having to listen to an old drinking buddy now spouting the craziest nonsense.
After? Your wording implies the breakdown has ended. :P
As to the original topic, I just checked my Youtube messages (I know I've been sent some choice stuff over the past 6 months) but unfortunately it only saves the last hundred messages... but essentially what happened was, with my fancy talk and heathen 'logic', I managed to trap a theist into either denouncing (part of) his faith, or admitting that he approved of torturing babies... and he chose torturing babies.
I've had several claim that even though the bible documents the Yahweh character personally slaughtering thousands, and commanding the massacre of millions - and these numbers of course ignore the Great Flood myth - that he has the "right to do so, because he gave us life and he can take it away, it's a gift and it is his right to kill us if he wants"... But then when I ask them if they think parents have a right to kill their kids, they get all backtracky :P
Another one admitted that his statements supported the idea that if his god demanded that he rape his grandma or a 12-year-old then a) he would have to do it, and b) it would be morally correct.
There's just no shaming some people into sensibility it seems. I guess all you can hope for after an argument like that (you know, the kind of ones where, when they come back with the ridiculous and in some cases reprehensible answer, you're just a bit stunned that they seem genuine about something so batsh1t crazy) is that although they profess certainty in what they're saying/typing, at least a part of them somewhere is saying "wait wait wait... what did I just say? That isn't right... is it?".
Thoughtful comments, Gliktch, amusing yet disturbing examples. Your last para is all I can hope for too. People do get very defensive and say the darndest things, but the truth has a way of getting under their skin after later reflection, so keep on punchin'.