I can't really say, any of those can be bad if handled badly.
I'd guess discrimination would be worst though, because it seems the easiest to learn and execute. It doesn't take a lot of effort or determination to be discriminative, as opposed to murder.
Overall, it's a case thing though. Games for teenagers without blood in them might actually have a better chance of making someone murder someone else, because the players don't see the consequnces of shooting/killing someone.