I don't know if it's the season or what, but the tasteless jokes just seem to be flying thick and fast:
Son takes his father to the doctor. Doctor gives them the bad news that the father is dying of cancer. Father tells the son that he has had a good long life and wants to stop at the bar on the way home to celebrate it.
While at the bar, the father sees several of his friends. He tells them that he is dying of AIDS.
When the friends leave the son asks, "Dad, you're dying of cancer. Why did you tell them that you are dying of AIDS?"
The father replies, "I don't want them fucking your mother after I'm gone!"