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Where two major columnists— David Brooks of the New York Times and Ruth Marcus of the Washington Post— went wrong when they weighed in on the debate over legalizing marijuana.

Responding to the first day of legal marijuana in Colorado, Brooks and Marcus made their case for what they believe was a misguided policy. While their arguments weren’t new— Brooks cited the anecdotal case of one of his pot-smoking friends who went on to become a “full-on stoner” —their indictments of legalization ignited the ire of writers and columnists on the other side. They happily circulated and ridiculed the essays on social media for their failure to reflect some of the latest data. Here’s where Brooks and Marcus crippled their own case:

1) By arguing that marijuana use is inherently immoral

Brooks focuses his opposition to legalization on the idea that marijuana smoking is “not a particularly uplifting form of pleasure and should be discouraged more than encouraged,” based, it appears, largely on the fact that he embarrassed himself during high school by smoking before a class presentation.

But why does this mean that marijuana should be illegal? Would arresting the teenaged Brooks have been a better way of ending his use than his own realization that it made him appear foolish? To ask the question is to answer it.

It’s hard to argue with a straight face that arresting Brooks would have helped. In fact, research shows that kids who are arrested and put into the juvenile justice system for any type of crime, including marijuana possession, are almost seven times more likely to have criminal records as adults than kids with similar levels of youthful misbehavior who are not arrested.

Our current laws already fail to deter around half of the population from trying marijuana by the time they reach adolescence. And black people are at least four times more likely than whites to be arrested for cannabis, despite the fact that they use and sell the drug at around the same rate as whites. If heavy arrest rates were a deterrent, blacks might logically have much lower use rates— and yet, they do not.

Is subjecting black people to potentially harmful arrests that do not reduce marijuana use a higher moral path for society than legalizing marijuana and applying more effective strategies, such as the successful methods that have reduced cigarette smoking? And to take this line of thinking to its natural conclusion, where is the morality in selling alcohol and cigarettes, both of which have been linked to known health and societal harms?

2) By maintaining that legalizing marijuana will lead to a dangerous increase in use

Both Brooks and Marcus fear that marijuana legalization will cause a tremendous and potentially dangerous spike in use of the drug. Writes Marcus, “[T]he more widely available marijuana becomes, the more minors will use it.”

But while legal sales can increase use, it doesn’t necessarily mean it would happen or that use would surge to higher levels than we have already experienced. Price is certainly a factor— and can be regulated with legal drugs. We can also look to other countries that have decriminalized marijuana, like Portugal, or those that tolerate some commercial sales, like Holland, for some idea of what might happen. Those countries actually have lower rates of marijuana smoking among youth than the U.S. does, even though they have allowed such use for many years. That suggests that while marijuana will still be illegal for those under 21 in Colorado and Washington, removing the illicit thrill of forever “forbidden fruit” might potentially discourage pot smoking.

MORE: Portugal Decriminalization A Success, Says Report

3) By remaining convinced that marijuana use lowers IQ

Marcus and Brooks also cite as fact the idea that marijuana use during adolescence lowers IQ. Although one study did suggest this, there are many reasons to be skeptical. A different set of researchers published a study in the same prestigious journal, suggesting that poverty could account for the association.

In addition, studies of marijuana and failure to complete high school are confounded by the fact that zero tolerance policies can cause kids to get expelled for smoking pot— which doesn’t necessarily mean that the drug contributed to impaired cognitive performance that led to their inability to earn a degree.

A study just published in the journal Drug and Alcohol Dependence also examined the links between early marijuana use, poor academic performance and drop out rates in a sample of over 3,000 twins. That analysis found that the connection was better explained by shared genetic or environmental factors that predispose students to both reduced school performance and early marijuana smoking— not to early use itself. The study did not specify what these factors might be, although other research suggests that poverty, childhood trauma and genetic predispositions to mental illnesses like depression are linked to both early drug use and to educational problems.

MORE: Study Questions Marijuana’s Effects on IQ

Finally, there’s the fact that around 10% of high school seniors during the late 70s and early 80s (a generation to which I belong) smoked pot every day— and yet, my colleagues don’t seem to be any less intelligent than boomers like Brooks.

It’s one thing to oppose legalization— there’s a coherent case to be made that no psychoactive substances should be sold directly to consumers by for-profit companies, for example— but if you are going to do so, it helps to engage with the data, wherever it may lead.