Now that is funny to me. Why? You are making my point when you think you are doing the opposite.Humor is art, not science....
And that is why most good humor is based in the truth or fact. The twist on it makes it funny, but as you said, when the premise is bogus and normally hateful, whatever follows is not funny.
Like when the Sexual Predator tried to tell the joke about Rush Limbaugh sticking up for someone. I cannot remember the set up, but the punchline was- "That's only because she was attacked by a black guy."
The premise for the ignorant who thought it was funny and hated Limbaugh was that Limbaugh was a racist because he was conservative and did not treat minorities with kid gloves. Those who actually listened to him knew he treated everyone equally. Heck, his call screener for thirty years, and two of his best guest hosts were black. Not quite the actions of a racist.