Because a bunch of people have for inexplicable reasons tied their meaningful parts of their self identity to Elon and his grievance filled simplistic worldview and they get very very upset when flaws in it are pointed out and they respond by trying to make sure nobody can publicly criticise it.
I would like to be generous and declare that it is due to the polarising nature of Elon Musk that the discussions end up degenerating into poor quality comments.
However, I don't personally believe that as even topics which are more to do with the products rather than the man seem to get flagged extremely quickly.