Are there topics you can't/shouldn't joke about? Why or why not?

At a friend's parent's dry cleaning business, the funeral director of the funeral parlor next door came in for his suit. When they asked him "how's business today" he said "oh, people are just dying to get in."

Yes, the funeral director actually said it. Can't believe he said it, but he probably thought it would lift the mood since he's worked there forever and they know him well. Dark humor? Definitely. Did my friend's parents laugh? Yes, nervously. Tasteful? Probably not.