Even when looked at from a progressive perspective I think what you're bringing up is a bigger problem to be honest. You're taking people who maybe think that

Even when looked at from a progressive perspective I think what you're bringing up is a bigger problem to be honest. You're taking people who maybe think that say, write shitty things about fat people or want to use that as motivation to lose weight and putting them in a basket with people who were subscribed to /r/niggers. Pushing people out of major communities over minor offenses only results in the promotion of more offensive views in those people. This kind of exclusion from the mainstream results in extremification of views in those individuals. I've felt it myself, I've found myself agreeing with things that I know mere years ago I would have outright rejected, but now contemplate. People don't back down on views like that, they just clamp down harder. So in my opinion it's a lot better to just argue with them and not to censor them.