Scrambledsmegs it was vile. One in particular. The OP asked for help on a very basic, practical issue and made it clear she didn't want to discuss the thinking behind her decision. This decision in no way made her a bad, irresponsible mother, was extremely personal, and was entirely supported by the relevant professionals.
People tried to "helpfully" challenge her decision "in case she hadn't thought it through". She reiterated that she wasn't in need of that, she just wanted info in a practical sense. People got angry that she wouldn't discuss her personal situation and justify her life choices. She said it was none of their business and she was happy with her decision. People started saying her attitude was disgusting and they pitied her child. She was upset and angry and said so. She was then told she was a vile human being and had brought it on herself. At that point I told people it was none of their bloody business and to butt the fuck out of her life and stop bullying her, and someone actually began to argue the dictionary definition of bullying as this was one thread and not a course of action and thus it couldn't be bullying! I pointed out she had confused employment grievance procedures with dictionaries for one, and two that if a dictionary definition was her best fucking defence to being a bullying arse, then she had no sodding defence.
Aaaand breathe. Lol. It was three years ago, I don't even remember the OP's name, never saw her before or (funny, this) since, but my heartrate still increases when I remember how she was treated. Several people did start to defend her, though. The thing is, her posting style wasn't especially likeable. But she wasn't a nasty, rude, aggressive or combative poster, she was just not a very open or MN style poster. And people kept saying they didn't like how she came across as a defence when told to stop attacking her. It was horrible, horrible, horrible. Truly upsetting and shameful to witness.
That is bullying. Not people having a stupid scrap on AIBU. I posted on a minor issue this week, namechanging so as not to IRL out myself, and I got some very arsey replies - but hey ho. Who gives a crap? Overall the views were useful to me, and if some idiots individuals can't read properly and misunderstand plain English, why, I am plainly vair superior to them anyway. 
No need to get hissy over it, especially as I know full well they'll be posting things that have me nodding with total agreement next week. Life is too short. Posters who engage in squabbles because they take umbridge with strangers not being meticulously careful with their posts are too fragile for the web, IMO. Certainly for AIBU.