I know this is in 'Chat', but you have titled your post as if it is following AIBU to.......... so no wonder people are saying, yes, YABU.
I read it all the time, and post sometimes.
I don't see posters "attacking other users quite openly in a way you never would in the real world". If you see a poster attacking another poster, then report it to MNHQ.
If, however, a poster says "AIBU to.......{ insert whatever they do or think}" ...... then they need to be ready to be told, "Yes, YABU". If you aren't ready, then don't ask.
If someone in RL asked me "Do you think IABU to {insert issue}?", and I thought they were, then I would tell them so. If they were just doing it, I possibly wouldn't - depending on situation.
If a person wants support, then there are plenty of other boards to use. If thy want advice or sympathy, there are plenty of other boards to use. If they want honest opinions, then they can use AIBU. If they are feeling vulnerable or very sensitive, then don't go around asking people for honest opinions as to if YABU or not - in RL or the internet.