Part of it is that purity tests are at an all time high. In large part because we are constantly inundated with Content to reinforce our world views (or the world view of the Influencer we glommed on to) constantly. So anything different is not just cognitive dissonance: it is an attack on our very core and a lie. So if someone does something we wouldn’t do? They are the evilest of evil people and are knowingly hurting whoever we care about.
But the other aspect? The internet is a great place to meet people with different life experiences. And in a lot of cases (particularly with certain politicians), we and the people we love have been directly harmed by them. All that steven universe bullshit about needing to love everyone and always finding the good goes out the window when you are increasingly watching organizations try to murder you for embracing who you are and to enslave people and turn them into breeding stock.
And the last aspect is that lemmy has a really bad infestation of tankies. Tankies who, useful idiots or intentional, tend to actively argue for destabilizing The West and increasing conflicts. So advocating for terrorism and murder helps with that.