More from me:
OP describes a family member with a long history of forgetting details, missing deadlines, endless clutter, other behavior that screams out possible ADHD. Other people tell OP that this family member is a selfish loser who doesn’t care and should be divorced/cut off immediately, with no one mentioning the possibility of ADHD.
Or, on the other side: OP describes a family member and gives one single example of this family member messing up something important. Without asking whether this is a pattern, other people assume ADHD.
OP, or OP’s relative, is pregnant in less than ideal circumstances. Although the post indicates that the pregnant woman intends to give birth, other people tell OP that the “smart” and “responsible” thing is to have an abortion. If the pregnant woman is the OP’s relative, people insist that OP sit this woman down and make her see that she needs to have an abortion.
OP holds a view that, while a minority view on Mumsnet, is fairly common among women. People insist that OP is really a man, because “every woman knows” or “no woman believes” full-in-the-blank.