I'm not sure of the origin of the phrase, but it sure is useful these days. In a discussion of the notorious New Yorker cover that featured the Obamas dressed up as terrorists as an example of hipster racism, AJ Plaid attributes the term to Carmen Van Kerckhove, and defines the phenomenon as "ideas, speech, and action meant to denigrate [another person's] race or ethnicity under the guise of being urbane, witty (meaning 'ironic' nowadays), educated, liberal, and/or trendy."
Plaid's definition fits a lot of hip, sardonic, or otherwise supposedly witty approaches to race, but I think it can be refined. For one thing, while most white practitioners of hipster racism do mean on the surface to denigrate another's race or ethnicity, their ultimate, ironic intent is to show that they don't really mean it, and thus, that they themselves are anything but racist. This seems to be how the upcoming Pauly Shore movie that I wrote about recently works, and as the clip below illustrates, it's sometimes how "The Daily Show" works.
The following skit, with John Oliver "traveling" to Kenya, is a good example. The segment begins as a trip meant to inform ignorant American viewers about the country that helped produce Barack Obama. When Oliver sits down with Zachary Muburi-Muita, the Kenyan Ambassador to the United Nations, the skit devolves instead into a sad instance of hipster racism, with Oliver playing a British moron who has no sense of what was wrong with England's racist colonial rule of Kenya.
As you watch, notice how at one point, when Muburi-Muita tells him that what's he's saying is "not funny," Oliver keeps going. In effect, a non-white voice of protest goes ignored and disrespected. Viewers hear Muburi-Muita's protest, but in the context of the skit, they're invited to laugh at it, and thus disrespect the person delivering it--"He can't even see that Oliver's joking! Look how far Oliver is willing to push this joke!"
As with other forms of satire, this type of humor goes wrong when it goes too far. In terms of race, one way that hipster humorists can go too far is by using people of color, who may or may not be in on the joke, as mere props in their own performance. By pretending to ignore the Kenyan ambassador's indignant response to a mock colonialist attitude, John Oliver demonstrates this failure. Whether the ambassador is in on the joke or not, the skit invites viewers to disregard and laugh at his perspective. That perspective is also trivialized because it's being used in a skit that's all about the performance of the white person at the center.
Self-reflecting irony of this sort is a crucial element of the hipster attitude, and as I understand it, hipster racism often arises in attempts at ironic humor. As Oliver demonstrates, this type of humor consists of acting like some sort of clueless, offensive bigot--be it a racist, a sexist, or a homophobe--for an audience that's supposed to know that you yourself are not really a bigot. You tell racist jokes or say and do racist things, but you're really making fun of bigots, so the humor is a supposedly legitimate form of satire.
White hipster humor about race is often meant to point out racism, but not in order to fight against it; the goal instead is ultimately narcissistic. The performance is an effort to get laughs, but it's also the comedians' self-centered effort to show that underneath it all, they themselves are not racists. This form of humor thus does little to dislodge the obstinate centrality of whiteness, because again, it's really all about the supposedly non-racist white performer, and not about the abuses endured by the targets of racism.
White people have a long history of defining themselves in opposition to the supposed inherent qualities of other races. When white people defined non-white people as savages, or as hypersexual, unintelligent or enslaved, they also defined themselves as the superior opposite--as civilized, restrained, intelligent, and free. In the same way, many white interactions with non-white people continue to be narcissistic, because they use non-white people to reflect back in a self-defining way on themselves.
When white hipster humorists perform a racial identity that involves interaction with non-white people, it's often all about the white person at the center. Using people of color so that you can pretend to be a racist in order to get laughs because you're mocking racists is not a genuinely respectful and anti-racist form of racial interaction. Instead, it's a way of acting in an ultimately racist manner, by using overt racism to suggest covertly, but falsely, that you yourself would never do anything racist. And since it's all really about you, and you're just using people of color for your own self-defining purposes, it amounts to little more than white self-centeredness all over again.