I try and remember on mumsnet (someone on here posted a link to a great cartoon about it...)
Normal person + anonymity + audience = total fuckwad.
There's no boundaries on here, often people don't give a shit about others' feelings or POV. They just want to vent or rant or be part of the majority or whatever. I think you need to be a bit prepared for it if you're on an AIBU thread, tbh, but what really pisses me off is getting flamed on other threads specifically dealing with that topic (i.e. pro-BFing, pro-HE etc).
You have to be quite tough on here