If Discord had "a major role" then wow - you'd put a huge burden on everyone who enables any kind of communication. All of them would have to implement a heavyhanded manual and automated censorship, with banning discussion of certain topics outright, use of machine learning to analyze sentiment... It would be the end of encryption (because if you don't combat encryption, you have a 'major role' in anything bad that happens).

Of course Discord has no responsibility in what people talk about on their system. Otherwise they should claim partial ownership on all good ideas that come out of it too.

I blame a divisive society pitting people against each other and allowing no middle ground, leading to radicalization, and the availability of guns that allow people to immediately act on their hate.