I’m not often a fan of essayist Joel Stein, the man who introduced narcissistic reportage into modern mainstream journalism. This week, however, his column on Trump in Time Magazine (June 6, 2016) was surprisingly on-target. Leaning heavily on the work of philosopher Joshua Knobe, Stein examined how mass opinion can influence and alter moral commitments. In particular, Stein examined how comments by Trump originally perceived as outrageously prejudiced and racist had –as Trump gained mainstream popularity –lost all shock value, and even gained the implicit endorsement of figures who had previously sought to distance themselves.

The thing you’re observing about Donald Trump is that people are thinking that being racist is in some weird way normal

- Knobe, as quoted by Stein

The truth, however, is that racism is –and not just in some weird way –normal. The majority of human beings throughout history have been horribly prejudiced against people of other groups, even in cases where those other groups differed from them in relatively minor ways (as with the ancient Jews and Samaritans, or as with the British and the French throughout much of their entwined history). What is exceptional is a sustained, widespread, mainstream moral commitment to repudiate racism, as was forged in America in the crucible of the civil rights movement.

Prior to the civil rights movement, many otherwise decent people, even some with liberal views and politics, blithely held views that were considered reprehensible just a few years later. What changed? The answer is that what had been previously viewed as “harmless” prejudice was, through the actions of the movement, exposed as inextricably linked to moral degeneracy and crimes against humanity.

When you think of a “racist,” do you think of a stocky, rage-filled white man with a deep Southern accent, willing to violently attack innocent people, including women and children, just because of the color of their skin? If so, the person you’re picturing is Eugene “Bull” Connor, onetime Commissioner of Public Safety for the city of Birmingham, Alabama. Overnight, he became the public face of racism for an entire generation, when he was photographed deploying attack dogs and firehoses against a crowd of peaceful protestors.

For a nation, that was the end of the myth of harmless prejudice. The civil rights movement had connected the dots. Prejudice was racism. Racism was the foundation of segregation. And under the sway of segregationism people had become so morally deformed that they were willing to murder not only the black people speaking out for their rights, but even the movement’s young white allies. Racism had made the nation critically ill, and repudiation of racism was the only cure.

Few enough people today have a living memory of Bull Connor, of the murder of young white civil rights activists, or of the church bombing that claimed the lives of four little girls. For a new generation, prejudice is more like an illegal drug –something you’ve always been told is horrible and dangerous, but that you’ve indulged in secretly, and really doesn’t seem so bad, something that provides a little forbidden thrill. If you get caught experimenting with it –like the frat boys recorded singing a ditty celebrating lynching –the grown ups punish you and make a big deal out of your “crime,” but it’s all just part of the hypocrisy of adulthood.

In that context, the open racism of a Donald Trump can appear as forward-looking as the marijuana-legalization movement of Colorado. Our outrage is empty, because we’ve forgotten how to connect the dots. We don’t remember that prejudice is racism, we don’t remember that racism is the foundation of separate-and-unequal, and we especially don’t remember that separate-and-unequal is harmful even to those who perpetrate it, let alone those who suffer under it.

In that context it’s important to remember why diversity is important. It’s not just a buzzword, or a box to check off on a form, or an enforced form of groupthink. The truth is that no one is safe in a society that rejects diversity, because no one is so close to the favored norm that they cannot find themselves one day in the out-group.

As philosopher Frantz Fanon described, racism is a really a psychological process of displacing unwanted negative traits from yourself to an out-group that you can distance yourself from. Once you tell yourself “I’m not lazy, I’m not stupid, I’m not violent, I’m not greedy, I’m not perverse, it’s all those [blacks/Jews/gays/Catholics/women/poor/etc.] coming in and ruining everything,” you lose your power to address your own flaws directly. All you can perceive to do is to attack, punish or oppress the scapegoated outgroup. But the process never ends, because once you get rid of one group, and discover you haven’t perfected your world, you have to find another group to identify as the problem. And history has shown us that no group is so homogeneous and alike that it cannot divide and turn upon itself.

Conversely, a society that embraces diversity is a society that is safer for everyone, and their own personal expression. You might not have any personal desire to change your gender, but if you attend a school that does its best to understand someone who does, it might have a little more understanding and support for you if you’re a straight boy who happens not to love sports, or a straight girl who does. If you live in a place that accepts and respects its citizens with black skin, then you don’t have to worry that tomorrow you’ll face discrimination based on your red hair.

Our collective commitment to diversity was won with such difficulty and at such high cost. If we throw it away, we may all live to regret it.