Reddit is designed to propagate content to the front page that invokes indecency. Take, for instance, a video of someone jumping turnstiles at a subway station or a homeless person bathing themselves in free hand sanitizer solution. What kind of comments is a video like this going to solicit?

If you want to keep things decent and avoid nastiness, prohibit content that evokes a strong emotional response. This strong emotional response, unfortunately, is what keeps people coming back.