Yeah, that's a problem. The thing about deleted comments is that they are still be visible to the person who posted them, so they could quote them when alerting others to censorship. The problem then is that people can lie. The downside to making deleted posts visible is that there can be very good reasons to keep posts invisible (e.g. somebody posting content that would be a legal issue or present physical risk, such as doxing).

I'm inclined to look at patterns. If somebody makes a habit of making insulting posts then it was probably deserved. If somebody has a decent history of posting, even if their views are contentious, then I'd be inclined to side with them.