It's not social media itself, it's social media companies tolerating the intolerant.
Back in the day nazis recruited at punk shows, so when they showed up you punched them in the face and they left. Fucking easiest 2 minute conflict resolution ever and it kept them check for decades while letting teenage punks have a valid target for their rage.
Then daytime TV (Springer, Ricky lake, that shit) started bringing them on, and letting them get their message out, and they capitalized on that with early webpages and forums. Creating the same recruitment pipeline they use today, because people can't physically punch them in the face online.
The mods/admins have to do that with bans.
When they don't, it's for the same reason as Springer. They want the conflict because conflict attracts eyeballs. But all it does is help nazis recruit.
There can't be any tolerance of the intolerant.