This is why I think downvoting submissions/comments is needed. I like how Hacker News forum does it. You need to have a certain number of upvotes on your contributions to even be able to downvote, and if the comment or a reply receives a lot of downvotes it gets greyed out or collapsed.
But again, ability to downvote is not enough, users needs to be aligned on what they want their community to look like. In case of HN, a very devoted and unique community, theres no patience for low effort, agresive and funny without a cause submissions. Their Guidelines itself is a really wonderful read.
It only gets more interesting with each day :)