People post for validation or genuine comprehension over an issue.
Replies go either way, agree or disagree, sometimes quite strongly. I've seen a lot of posts were OP has been flamed and wished they had never posted. I've been there, under a different name. I've asked Mumsnet to have more moderators, to keep things on track but I guess that wont happen. I've seen a few posts get mentioned on DM recently and think, thank god that wasn't me! Some posts get quite out of hand and once one negative post starts, other pile on.
YANBU - to think people should stick to the question asked and not unpick every single thing.
YABU - people will naturally be critical because it's on-line and not face to face and why post on a public forum if you can't handle it.