One of the features of all the Ferguson discussion over the past few months is how tinny the comparisons to the civil-rights era have sounded. People have tried to link Ferguson to Selma and Jim Crow, but something is off.

That’s, in part, because we’ve moved from simplicity to ambiguity. The civil rights struggle was about as clear a conflict between right and wrong as we get in national life. The debate about Ferguson elicited complex reactions among most sensible people.

This complexity was best expressed in the short essay that Benjamin Watson, a New Orleans Saints tight end, posted on Facebook, which went viral. Watson listed 12 different emotions the Ferguson mess aroused, including:

“I’m ANGRY because stories of injustice that have been passed down for generations seem to be continuing before our very eyes. ... I’m OFFENDED because of the insulting comments I’ve seen. ... I’m INTROSPECTIVE because sometimes I want to take ‘our’ side without looking at the facts in situations like these.”

But the other reason that the civil-rights era comparisons were inapt is because the nature of racism has changed. There has been a migration away from prejudice based on genetics to prejudice based on class.

Let me explain with a historical detour. In 18th- and 19th-century Britain, there was a division between “respectable” society and those who lived in slums that were sometimes known as rookeries (because the neighborhoods reminded people of rock faces where thieving crows lived in little nooks and crannies).

The people who lived in these slums were often described as more like animals than human beings. For example, in an 1889 essay in The Palace Journal, Arthur Morrison described, “Dark, silent, uneasy shadows passing and crossing . human vermin in this reeking sink, like goblin exhalations from all that is noxious around. Women with sunken, black-rimmed eyes, whose pallid faces appear and vanish by the light of an occasional gas lamp, and look so like ill-covered skulls that we start at their stare.”

“Proper” people of that era had both a disgust and fascination for those who lived in these untouchable realms. They went slumming into the poor neighborhoods, a sort of poverty tourism that is the equivalent of today’s reality TV or the brawlers that appear on “The Jerry Springer Show.”Today we once again have a sharp social divide between people who live in the “respectable” meritocracy and those who live beyond it. In one world almost everybody you meet has at least been to college, and people have very little contact with features that are sometimes a part of the other world: prison, meth, payday loans, a flowering of nonmarriage family forms. In one world, people assume they can control their destinies. In the other, some people embrace the now common motto: “It don’t make no difference.”

Widening class distances produce class prejudice, classism. This is a prejudice based on visceral attitudes about competence. People in the “respectable” class have meritocratic virtues: executive function, grit, a capacity for delayed gratification. The view about those in the untouchable world is that they are short on these things. They are disorganized. They are violent and scary. This belief has some grains of truth because of childhood trauma, the stress of poverty and other things. But this view metastasizes into a vicious, intellectually lazy stereotype. Before long, animalistic imagery is used to describe these human beings.

This class prejudice is applied to both the white and black poor, whose demographic traits are converging. But classism combines with latent and historic racism to create a particularly malicious brew. People are now assigned a whole range of supposedly underclass traits based on a single glimpse at skin color.

During the civil-rights era there was always a debate about what was a civil-rights issue and what was an economic or social issue. Now that distinction has been obliterated. Every civil-rights issue is also an economic and social issue. Classism intertwines with racism.

It’s often said after events like Ferguson that we need a national conversation on race. That’s a bit true. We all need to improve our capacity for sympathetic understanding, our capacity to imaginatively place ourselves in the minds of other people with experiences different from our own. Conversation can help, though I suspect novels, works of art and books like Claude Brown’s “Manchild in the Promised Land” work better.

But, ultimately, we don’t need a common conversation; we need a common project. If the nation works together to improve social mobility for the poor of all races, through projects like President Obama’s My Brother’s Keeper initiative, then social distance will decline, classism will decline and racial prejudice will obliquely decline as well.

In a friendship, people don’t sit around talking about their friendship. They do things together. Through common endeavor people overcome difference to become friends.