Earlier quoted context omitted.
It's not some theoretical 'divisive', you can read how these threads go yourself, including this one. The meta discussions also make these a lot worse so it's hard to blame this on some 'small number' of people.
A lot of the flagged posts look completely fine, to me. Basically the entire discussion is greyed out, which suggests a pretty intense unwillingness to talk about the subject on principles alone. I think by playing the brinksmanship card of "there can be no level-headed discussion" you inadvertently discount a lot of perfectly coherent and important digression, on both sides. If every HN thread resorted to this logic…
Some comments that clearly break the rules should be removed by the community. But that should take multiple downvotes.
The flagging just allows one or two people to remove a part of the discussion, and we rely on other users to view dead or flagged comments to “rescue” them