There has been a lot of discussion about the racism and misogyny inherent in the joke. All that analysis is true. It's racist and misogynistic. But that misses the point. The point is that it's dirty and tasteless.
When I was a kid I had a trove of treasured joke books from a series called, "Truly Tasteless Jokes." The aim of the punch lines is to make you wince. The more you wince, the more you laugh. That's the point.
Anyhow I wanted to see if I could prove that Judge Cebull's joke was an old one. So I did a search for the punchline ("you're lucky you don't bark") in Google, with a custom date range from 2000 - 2010.
The second result was a 2009 interview of Willie Nelson in Vanity Fair. Here's relevant part (with the interviewer's questions in bold:
You wrote a book called The Facts of Life and Other Dirty Jokes. What's the dirtiest joke you've ever heard?
Hmm. (Long pause.) See, my idea of a really great dirty joke isn't something you can share with everybody. You gotta watch yourself.
Come on, you can tell us. We won't judge you.
Well, one of my favorites goes something like this…. A kid asks his mama, "How come you're white and I'm black?" And she says, "Honey, from what I can remember of the party, you're lucky you don't bark."
(Laughs.) Wow. That is good. But you're right, probably not for everybody.
You gotta be careful. Not everybody can appreciate a funny goddamn joke.Bingo.