Riots and looting in Ferguson, Missouri, over the shooting of 18-year-old Michael Brown by a police officer represent just the latest spate of race-based mass violence to break out in President Obama’s post-racial America. When Obama was elected in 2008, many Americans hoped that racial conflict in the country would calm. Instead, precisely the reverse seems to have occurred.

Not all riots across the country have been racial in nature, of course. Occupy Wall Street participated in riots repeatedly in 2011, and May Day protesters rioted in Santa Cruz in 2010 and Seattle in 2013, for example. There have also been repeated riots on college campuses over incidents ranging from sporting events to frat parties.

But with every controversial police shooting of a minority victim, the possibility of riots looms these days. That’s been true since well before President Obama took office, thanks to a racial grievance industry based on the tacit threat of violence. But President Obama has done little to tamp down that industry and much to energize it.

Aside from the current violence in Missouri, here are the worst mass racial violence incidents of the past few years:

Oscar Grant Riots. In 2009, shortly after President Obama’s election, police officer Johannes Mehserle shot black transit passenger Oscar Grant in Oakland, California. While Mehserle was found guilty of involuntary manslaughter in 2010, rioters took advantage of the situation anyway, trashing police cars and forcing Mayor Ron Dellums to take shelter in City Hall. Local businesses were vandalized. In the end, some 120 arrests were made. That violence was not the first surrounding Grant’s killing – right after Grant’s killing, rioters engaged in vandalism, as well as attacks on a police officer. Grant’s mother told the media, “I am begging the citizens not to use violent tactics, not to be angry. I know it’s a very frustrating time, but Oscar would not want to see all the violence that’s going on. He would not want to see the fires, he would not want to see this. You’re hurting people who have nothing to do with the situation.”

Trayvon Martin Violence. After George Zimmerman was acquitted of murder in his shooting of black teenager Trayvon Martin, local rioters in Los Angeles began “stomping cars and breaking windows.” A television reporter and cameraman were assaulted by a crowd of criminals. Looters attempted to break into a local Walmart. About 150 criminals took part in the riot. In San Bernardino, eleven protesters were arrested after throwing bricks at passing cars. A white man was robbed by three black men in Washington, D.C., and was allegedly told by his assailants, “This is for Trayvon Martin.” In Baltimore, a Hispanic man was allegedly chased by a mob of black youths shouting, “This is for Trayvon.” President Obama said regarding Trayvon Martin during the ongoing investigation, “My main message is to the parents of Trayvon Martin. You know, if I had a son, he’d look like Trayvon.” Obama’s Department of Justice even headed to Sanford, Florida, to pursue an investigation against Zimmerman.

Manuel Diaz Violence. After 25-year-old suspected gang member Manuel Diaz ran from police and was shot to death in 2012, local residents began throwing objects at police officers. Soon, that situation escalated, with the Orange County Register reporting, “At least five people were reported hurt in the unrest, with crowds setting fires, smashing windows and throwing rocks and other projectiles at officers in riot gear who fired non-lethal rounds at demonstrators refusing to disperse.”

Kimini Gray Riots. When 16-year-old Kimani Gray was killed by police after allegedly pointing a handgun at them, riots broke out in Brooklyn in 2013. A crowd of 200 people, according to the New York Daily News, left a vigil site chanting, “NYPD, KKK, how many kids did you kill today.” Then things really went wrong: “things quickly got out of hand as some protesters tried to climb on police motorcycles. Men and women were pepper-sprayed and thrown to the ground and handcuffed.” That incident followed a similar vigil gone wrong the night before, when according to the NYPD, “a large, disorderly group [began] throwing bottles at police.” The crowd in that incident trashed a Rite Aid and robbed the store. Storefronts were also smashed.

These are incidents of mass violence, not merely individual crime incidents. And such incidents are testimony to the continuing sense of racial injustice purveyed by the media and the Obama administration.