Not everyone is going to be reading the replies. If people see racist topics on the front page and they can only see the upvotes next to it they probably won't bother clicking on the topic. At the same time, I don't believe downvotes are a solution because of what you said, people should be encouraged to discuss topics not just click and move on, also downvotes give rise to brigading which ends up serving the same function as censorship. Having a disagree emoji would be a good way to make sure the front page represents the reality of the site, so normies would bother to click further instead of just running away because they feel like everyone here agrees with that stuff.