Smart people tend to believe that social customs are arbitrary and that they could engineer better societies if only they held power. This type of thinking goes back to Plato claiming that philosophers should be kings. They don't understand that tradition has a wisdom inherited through the generations greater than any individual autist can invent.
Taboos against extreme racism and eugenics exist because, for all their high hopes about human improvement, they resulted in collective hubris and fanatical violent. The far-right hasn't learned from history. Likewise, Communism is mistrusted because it also had "good intentions" that spectacularly failed and resulted in mass murder every time they were tried. But a lot of heavy internet users lack empathy and don't even care about murder being wrong anymore so long as it serves their posturing, power fantasies, and parasocial sense of political belonging. I suspect that many of them know deep down that a shift to Fascism or Stalinism in the modern west would do nothing but destabilize the world and fuck things up horrendously, or that they could easily be the next Strasserists and Trotskyists that are purged after a "glorious" social change, but they're deluding themselves and they've built up identities in retarded echo chambers that reinforce their heroic identities.