“That’s racist.”

It’s a comedic catchphrase these days, popularized by an online clip from a 2005 TV show “Wonder Showzen” on MTV2. It’s not as iconic as Gary Coleman’s “What ‘chu talkin’ ‘bout, Willis?” or Fonzie’s “Ayyyyyy” or even Bart Simpson’s “Don’t have a cow, man.” But what it lacks in pedigree, it makes up for in ubiquity and social relevance.

Across the country, it’s a staple of schoolyards, Internet discussion groups, Twitter and sitcoms.

For instance, when a character on NBC’s “Parks and Recreation” explains to a co-worker how to do laundry, he says, “OK, so you always separate your lights from your darks.”

She responds, “That’s racist.”

Perhaps the greatest sign that the punch line has gone mainstream came last week when NPR’s “All Things Considered” reported on “that’s racist.” Correspondent Neda Ulaby explored how a phrase once considered one of the most serious accusations possible has become a gag line. The only problem? It’s not clear she actually gets the joke.

Ulaby relied heavily on Regina Bradley, who teaches African-American literature at Florida State University. Bradley admits her students say “that’s racist” all the time: “They were simply using it to lump discussions of race and race discourse all together. Because they were just saying because we brought up issues of race that was considered to be racist.”

OK, so apparently the reason these kids say “that’s racist” is that they’re not too bright. But, wait, there’s more. According to Ulaby, Bradley also believes that the students are using the joke to establish up front that they themselves aren’t racist. Good for them!

Hold on, another explanation is that kids simply mimic the stuff they see on TV shows like “30 Rock” and “South Park.”

I don’t want to overanalyze, but it seems as if everyone’s bending over backward to come up with the least obvious explanations for a pretty obvious joke.

For instance, here’s Ulaby again, talking about Hannibal Buress, a comedian and writer for NBC’s “30 Rock,” who uses the phrase: “'That’s racist’ works in comedy, Buress says, because it pushes buttons.” OK. How does it push buttons? Why does it push buttons?

We’re never told. Instead, we get a NPR tutorial on the persistence of racism. “Scholar Regina Bradley says it also works because racism’s often expressed differently than from a generation or two ago,” Ulaby explains. “The segregated neighborhoods and swimming pools of Bradley’s grandparents have yielded to more subtle forms of discrimination. That’s reflected in how ‘that’s racist’ is being used – to shut down conversations or as a joke.”

But what’s the joke? We don’t find out until a 14-year-old-boy says it plainly: “I think I or other people just sort of do it as a way of mocking people who are overly sensitive about race issues.”

Bingo!

NPR could have done the whole story in 30 seconds. But instead it spent more than five minutes trying to grapple with a wonderful yet utterly inconvenient truth for the ostentatiously liberal network: Young people just aren’t as uptight about race as their parents, never mind their grandparents, are. And, by the way, the days of segregated swimming pools and neighborhoods haven’t merely “yielded” to “more subtle forms of discrimination”; they’ve yielded to – wait for it – less discrimination.

No, racism hasn’t vanished. And the legacy of racism still has a long half-life.

But the simple fact is “that’s racist” is the sort of thing those darn kids today say to make fun of their aging Gen X and baby boomer parents.

It’s also a common joke among conservatives, precisely because we’re used to being called racists for the weirdest things. If I write on Twitter something about how I don’t like “Obamacare,” some fellow right-winger will immediately respond with some variant of “that’s racist!”

And that’s the joke. And the people who’ve spent the last few decades screaming, “That’s racist,” not as a punch line but as a heinously unfair accusation or in an attempt to bully people, don’t seem to get that the joke is on them.

© 2011 Tribune Media Services, Inc.