Back in the early 2000s there was a thing called the Yahoo Message Boards. I was on there running discussions about science fiction and horror movies. I was on there for about two maybe three years. In real -time, I watched those boards get infiltrated, one could even say infested, with more and more bigotry, racism, trolling, and just all-around sheer assholery. And it's happened in every other online space place humans congregate especially if there are no mods and people don't have a good ability to block trolls.
Remembering what I saw happen there, I never made any effort to get on Twitter and I quit Facebook after the information scandal broke. I wanted to see if what happened on Yahoo, happened on Twitter and I was right. Sooner or later all social media seems to devolve into its lowest common denominator or become infested with people who do nothing but cause harm and drama. Ive seen this happen on commentary sites, on Thought Catalog, Facebook, all of them. Some websites even went so far as to shut down their entire comment sections.
I like Mastadon's approach. When people act up on there it's a lot easier for the moderators to just cut their entire site loose rather than relying on individuals trying to block them.