Well, its unfortunate, and you can’t really blame a girl who has a mental health issue, but you can’t jeapordise the safety of an aircraft just to avoid hurting the family’s feelings.
I’ve seen the meltdowns that autistics have, pretty dangerous. However I viewed the tape another passenger made. Those people were crammed in like sardines! Tell me how that girl was going to harm anyone in such little space much less open the cabin door?? Oh please. The child was pinned against the window with both her parents. Most she could do was scream like an opera singer and from what I’ve heard a lot of babies on board do far worse.