Someone I know from the high school I graduated wrecked and was killed in the accident. **** YOU!
Unfortunately, if we are going to have to make things that could possibly offend someone off limits, as Spelt says, we won't really have anything to say for it will always happen. We have no idea what will send some people off, or what is associated to awful/traumatic experiences a person has experienced/been around. We just have to work with what we know, and we can't always know everything.
It's true I think it is less agreeable to make certain topics and words off limits than to say things that have a higher probability of making people feel hurt (like ****), but that does not mean it makes much sense to use such words all of the time and roll the dice and hope no one demands you to watch your mouth. It is too bothersome and not worth it to try and get away with some things. There are better ways to joke. Just because it is wrong to tell people not to say certain things doesn't mean we have to enforce it, the world isn't perfect, and although it could be considered flawed thinking to act imperfect to fit the imperfection of humans, but that is what you get for trying to incorporate the man-made idea of morality with the world.
Not sure if what I just typed makes much sense, but it took too much time, so I'm posting it.

Closing comment, just because people joke about a topic, contrary to popular belief, doesn't mean they don't take the topic seriously. It's common for us to make light of things that cause us grief and hit us hard.