Offensive comments are morally relative, though. Someone has to be offended, right?

In your examples, the victim certainly notices and cares; if they get a vote, they're going to vote "immoral." But if you did something "murderous" in absolute privacy--like, say, doing some target shooting--I don't think it would be considered equivalent to murder. Similarly, if you do something "offensive" and nobody is there to get offended, I don't see what the crime is.

Would it upset you if people were saying offensive things quietly to themselves in the privacy of their own homes? How would you propose to deal with that?