The family of Trayvon Martin, the 17-year-old boy who was killed last month in Florida by a neighborhood watch volunteer, confirmed on Monday that he had been suspended from school for possession of a trace amount of marijuana. In a news conference, Martin’s mother, Sybrina Fulton, accused authorities of leaking the information, along with details of the shooting, in order to demonize her son’s memory.

“They’ve killed my son and now they’re trying to kill his reputation,” said Fulton.

Can it be long now before the boy’s possible history of drug use is cited as justification for the self-defense claim put forth by the killer, George Zimmerman? According to Zimmerman’s account of the shooting, Martin, who was unarmed, violently attacked him from behind, leading Zimmerman to cry out for help before shooting his aggressor.

But Martin’s possible experimentation with pot should be no threat to his reputation. The research on marijuana and violence shows clearly that the drug either reduces aggression or has no effect — findings that fall in line with pop culture’s mellow image of stoners. The idea that marijuana makes people dangerous is as absurd as the claim that wearing a hoodie is suspicious.

Despite its widespread use — nearly two-thirds of the adult population aged 21 to 54 has tried marijuana at least once — more than eight decades of reefer-madness propaganda have served to obscure the facts about the substance and who uses it. Indeed, most antidrug campaigns have stigmatized not only drugs, but their users as well.

Here, it’s useful to remember that the nation’s vehement antidrug rhetoric is rooted in explicit racism. For example, the first state laws banning cocaine were passed in response to media reports about how the drug made black men homicidal, prone to raping white women and, worst of all to the police, impervious to bullets. An article about the issue in the New York Times in 1914 was headlined “Negro Cocaine ‘Fiends’ Are a New Southern Menace.”

Similarly, the first state legislation banning opium was linked to fears of Chinese men allegedly using the drug to seduce white women.

The campaign for national marijuana prohibition, which came in the 1930s, involved racism against both African Americans and Mexicans. One advocate of banning the drug wrote in the Times in 1935: “Marijuana, perhaps now the most insidious of our narcotics, is a direct by-product of unrestricted Mexican immigration. … Mexican peddlers have been caught distributing sample marijuana cigarets to school children.”

These days, the racism surrounding drugs is less obvious, but no less real. I experienced a vivid illustration of this myself in the late 1990s, when I appeared on Oprah to discuss Bill Moyers’ PBS series on addiction; I was a guest on Oprah’s show, as well as an associate producer of the PBS series. The first hour of Moyers’ documentary included a montage of clips from interviews with nine people with addiction, a group I’d booked with an eye to diversity of race, class and recovery experience. Moyers decided to include me as one of the interviewees.

On Oprah’s show, her other guests included Bill Moyers, his son William who is a recovering addict, along with another white female addict who appeared in the documentary. To open the show, Oprah displayed photos of everyone I’d included in the original documentary and asked the audience to see if they could pick out those who suffered from addiction. The audience overwhelmingly selected the black men — and, remember, this was Oprah’s audience, not one likely to be selected for its overt racial biases.

It still surprises people to learn that in the U.S., African Americans and whites take drugs at about the same rate, but black youth are twice as likely to be arrested for it and more than five times more likely to be prosecuted as an adult for drug crimes. In New York City, 87% of residents arrested under the police department’s “stop and frisk” policy are black or Hispanic. As Michelle Alexander writes in her bestselling book, The New Jim Crow: Mass Incarceration in the Age of Colorblindness:

In the era of colorblindness, it is no longer socially permissible to use race, explicitly, as a justification for discrimination, exclusion, and social contempt. So we don’t. Rather than rely on race, we use our criminal justice system to label people of color “criminals” and then engage in all the practices we supposedly left behind.

The drug war and the stigma it imparts on users are key weapons here. America’s cultural images of drug-related danger continue to be racially charged and the resulting stereotypes appear to be becoming increasingly deadly. Martin’s is not the only case in recent months to involve an unarmed boy and marijuana: three weeks before the Florida teen was killed, another unarmed black teen was shot to death by police, who chased him into his Bronx home. The young man was found in possession of a small amount of marijuana.

Attempting to address the problem is difficult. Recently in the U.K., a drug policy reform group stirred controversy when it launched a campaign to reduce the stigma of drug use. “Nice people take drugs,” was the slogan the group used in its ads, but even in a country that is much less punitive than the U.S. toward drug users, the posters were pulled from buses not long after the effort was launched, in 2009. The phrase was seen as potentially encouraging drug misuse by youth.

There’s no denying, however, that being nice doesn’t preclude drug-taking. Probably all of us can name someone we respect or admire who has taken illegal drugs. And most drug users — even those who favor cocaine, methamphetamine or heroin — are not violent. Indeed, the drug most likely to lead to violent behavior is not illegal: it’s alcohol.

If we want to avoid tragedies like the Martin case, we must confront the racism and class prejudice that infect our ideas about drug users and warp our view of how drugs work. We need to admit that drug use itself doesn’t make people evil. Perhaps if we weren’t so quick to let these biases demonize drug users, Trayvon Martin might still be with us.

If Martin’s school had not suspended the boy under its “zero tolerance” policy for drug use — one that punishes students for possession of an empty plastic baggie with trace amounts of marijuana as severely as for possession of heroin or a gun — he probably would never even have crossed paths with the man who shot him. Martin was serving his suspension on Feb. 26, when he was killed.

Such school policies have not been shown to reduce drug problems, but they, too, have been found to be applied more often to black youth. A recent analysis showed that black children are 3.5 times more likely than whites to be suspended from school for drugs and that 70% of all youth referred by school authorities to police for prosecution are black, even though they make up only 18% of the school population in the U.S.

Marijuana smoking certainly doesn’t warrant expulsion from school — never mind death. A general principle of drug policy is that the punishment should not do more harm than the drug itself. If we rewrote drug policy with an eye to marijuana’s actual danger, it would not warrant the loss of kids’ educational opportunities nor criminal penalties for possession, let alone suggest a rationale for being gunned down while walking home.

Maia Szalavitz is a health writer for TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland‘s Facebook page and on Twitter at @TIMEHealthland.