I would say its ok, as long as its clear you don't really feel that way. Usually the joke is so ridiculous that no one with a sense of humor would take it seriously, so you're probably fine. Of course, southpark and family guy go out of thier way to try to push the boundries of what can be made funny. If you are comfortable doing that then go for it, but keep in mind that jokes like that will cause people to view the game as "edgey"
I'd have to see the joke in context to determine if it is funny or in bad taste, but my guess is that its ok since you don't seem to be the type who tries to go for the shock laughs.