Number one: Plausible deniability:
You never can tell who is actually racist behind the keyboard and who isn't. If you see someone make humor at the expense of every race except their own, it's not humor. That's racism. Mel Brooks? Aziz Ansari? Gabriel Iglesias? They all make humor at the expense of their own race as well. They don't single out anyone. Of course, you shouldn't make light of this either and say "I'm not racist, I hate everyone equally." None of them said that. Ever. So, in conclusion on this point, someone could say "It's just a joke, I'm not really racist." But then, anyone could say that, couldn't they? Better to be on the safe side and "shun all appearances of evil." A quote from the bible the right wing loves to thump but fails to practice.
Number two: Gateway racism... rather, discriminatory humor (against women, homosexuals, people of color) is a gateway to leaning into these beliefs. I've seen it countless times that people claim they aren't the way they suggest. Yet, they become so comfortable with the humor, they forget to walk the line carefully and observe said line and they slip up.
Number three: When you make jokes at the expense of other races, you really don't know the impact you're having on them when you make these jokes. You can't know the impact as you aren't that race. You haven't lived every day of that race to understand what they go through.
If you really want a more educated and informed reflection on the matter, I highly encourage reading this:
https://theconversation.com/psychology-behind-the-unfunny-consequences-of-jokes-that-denigrate-63855
This website uses an example from Dave Chappelle when he said:
"I’m here at the Academy Awards, otherwise known as the White People’s Choice Awards. You realize if they nominated hosts, I wouldn’t even get this job. So y’all would be watching Neil Patrick Harris right now."
It eloquently and efficiently depicts what kind of humor is taking place when and where. It also references these jokes:
"Q: Why did the woman cross the road?
A: Who cares! What the hell is she doing out of the kitchen?
Q: Why hasn’t NASA sent a woman to the moon?
A: It doesn’t need cleaning yet!"
I'm not here to put people down for being racist or making racist jokes. But when people refuse to even consider the alternative, that's where the rub comes in. Dark Humor has a long history of racist jokes via plausible deniability. Often at the expense of everyone but straight white males.