That's exactly my point. I myself am not racist, nor do I believe in segregation, but does that mean I or others should actively work to prevent the discussion of those ideas? Wouldn't we become just as bad as the people we decry if we tried to suppress their viewpoints?
But I think suppressing a viewpoint is counterproductive. Instead, the holders of those viewpoints should be held to the light, and it's a Twitter problem in that such people can be completely anonymous or even fake. Hard to have a public debate when some of the participating citizens are fictional.
Yes, and no? Proposing racial segragation is something is highly offensive to non-white people, discriminatory in and of itself. If you're an employer, letting some guy talk about his beliefs in racial discrimination in your workplace is creating a hostile environment for your other employees. If you have any kind of position in a community, you shouldn't allow it there either.