It's easy enough to say that something isn't funny (such as above when someone said lighting someone on fire can never be funny) and another thing to view it as part of a whole (say, the South Park episode where Kenny dies after lighting his fart on fire).
When we think of someone being lit on fire, without context, we typically think of a real person with thoughts and feelings and emotions as they feel very real pain and anxiety - and that's good! We have empathy! Sympathy!
But when it's done in a clearly comedic situation, we're not asked to feel that sympathy because we know it's not real, no one is suffering.
Everyone has rights not to find certain jokes funny, or to find certain jokes to be off limit, but I think we all need to accept that these are simply our personal limits and others may not find them as offensive.
For instance, in watching one episode of South Park (since I mentioned it above), I got really offended. It was the The China Problem episode. Firstly, I hate when rape against men is used as a humorous thing, but I was okay with the episode - until the scene where Indiana Jones was raped in a bar, on a pinball table, while others cheered.
Why did this bother me? Because it was based on a movie that was based on a true story. A woman was gang raped on a pinball table in a bar, and as she cried for them to stop and for someone to stop them, no one did.
But... there was a lot of things in that episode that I could have just as easily found offensive, and I recognize that, no matter how I feel about gang-rape jokes never being funny, someone else will feel about something else not being funny.
There's a lot of situations that, when real, are heartbreaking, but comedians push the boundaries and many are extremely offensive. Laugh at the things you find funny, don't laugh at the things you don't find funny, but in the end it's best to just not let it bother you too much. We all have our own personal limits, but that's just what they are. Personal reasons.