If you're happy about a death, nothing is going to change that. I'm sure you will still feel the same way regardless of what you post, and I'm sure others probably know how you felt because of how you posted when the person was alive.
Letting people know that you're happy someone is dead doesn't change anything either. It lets people know that you still feel the same way, and you're not really concerned about appearing respectful.
While you may find this liberating, this kind of discourse actually produces the opposite result than what you may have anticipated. For example, a person from Fox News browsing these kinds of comments on social media would have another story with which to feed their hungry viewership about the hateful left.
I can't really think of anything good that was accomplished on someone else's tombstone except maybe a sense of relief in the case of the tyrants and murderers. Certainly nothing to be gained concerning this guy.