It's the latest instance of black-on-white mob violence sweeping America -- and a YouTube clip of the attack has gone viral. It shows a 17-year-old boy in Memphis, Tennessee, getting punched, knocked to the ground, and kicked in the head while lying helpless. Jubilant shouts and laughter from the black mob can be heard in the background.

The YouTube video shows a white youth -- an employee of a Kroger supermarket -- stepping outside the store's front doors last Saturday evening as a mob of black youths rampaged through the parking lot terrorizing shoppers. Reportedly, the mob was playing a version of the so-called "knock-out game" -- with this one called "point'em out, knock'em out." For one insightful news report, click here.

Thankfully, security people quickly showed up, saving the youth from potentially fatal blows. The attack was eerily similar to one inflicted upon an 18-year-old white college freshman at a McDonald's in College Station, Texas -- an assault that was the subject of a recent American Thinker article ("Beaten to Death at McDonald's") that went viral on the web.

In that case, McDonald's was ordered to pay a $27 million judgment for its lack of late-night security at its outlet near Texas A&M University -- the scene of large gatherings of young and often violent black males. Also killed that night was the beating victim's 19-year-old girlfriend, who died in a car wreck on an ill-fated attempt to rush her dying boyfriend to an emergency room.

Interestingly, a number of readers commenting on that American Thinker article brought up the case of former National Review columnist John Derbyshire, whose controversial article on race relations included advice that whites should avoid large groups of blacks -- unless they know all of them personally. Yes, some of Derbyshire's ruminations in "The Talk" could have perhaps been toned down; yet it can't be denied that if those two white youths at that McDonald's had taken his advice, they would be alive today. Well, no matter: National Review fired Derbyshire for that article at another publication.

Such Derbyshire-like observations also were raised in an allegedly racist e-mail that triggered the recent downfall of Atlanta Hawks controlling owner Bruce Levenson. In an apology, he wrote: "I trivialized our fans by making clichéd assumptions about their interests (i.e., hip hop vs. country, white vs. black cheerleaders, etc.) and by stereotyping their perceptions of one another (i.e., that white fans might be afraid of our black fans). By focusing on race, I also sent the unintentional and hurtful message that our white fans are more valuable than our black fans."

Though politically incorrect, Levenson was spot on when he suggested that many blacks and whites now inhabit two irreconcilable worlds. You have to wonder, incidentally, if there would have been a scandal if Levenson had stated that the NBA needed to draw more black fans to its basketball games.

What has happened? This was supposed to be post-racial America: our hip black president told us so. Yet black-on-black violence is now soaring to record heights --and black-on-white violence comes in a close second, and seems to be growing. You won't, however, read much about an upsurge of black-on-white crime in the mainstream media. Certainly not in College Station, where there was a media blackout about how a black mob stomped a white youth to death at a local McDonald's. And nor is black-on-white violence being widely discussed in Memphis, where some local news outlets have tiptoeed around the race of the assailants and victim in the attack at a Kroger supermarket. 

Perhaps Attorney General Eric Holder can head to Memphis to investigate this hate crime after he wraps things up in Ferguson.