“In its everyday operation,” sociologist James Loewen wrote, “segregation consists of a pervasive system of etiquette.”

That’s a counter-intuitive definition. Discrimination, especially the pervasive discrimination of the Jim Crow era, tends to be remembered as a matter of violence, not as a matter of manners. Jim Crow involved lynchings, beatings, and the KKK—politeness and etiquette seems like secondary matters at best. And yet politeness and violence are in fact intertwined and inseparable. Segregation was accomplished through an elaborate system of norms about when black and white people could meet, and how they could interact.

“Biracial segregation forms a complete set of definitions, expressing and codifying the relationship of dominance and subservience,” Loewen argues. This is ultimately enforced by laws and violence, when necessary—but often it’s more subtle, involving disapprobation, disapproving looks, cutting remarks, and (as Mark Twain described in Huck Finn) internalized shame. Institutionalized hatred is not just formal large-scale violence or legal rules. It is also the small-scale sneers and corrections and social coercion which normalize and justify that violence. Discrimination is, in brief, petty stuff. It’s etiquette.

Trevor Noah is currently mired in a welter of petty stuff. Noah, a South African comedian, was picked to succeed Jon Stewart at the helm of The Daily Show. Shortly thereafter, the internet unearthed a number of tweets in which Noah made anti-Semitic and misogynist jokes.

I should probably put that word “jokes” in quotes; the tweets are little more than tedious ritualized restating of stereotypes: Jewish people are rich, “fat chicks” are unattractive. Still, no matter how unfunny they are, a couple of bad social media jokes are only a couple of bad social media jokes. Compared to actual apartheid (which was abolished during Noah’s lifetime) they seem relatively minor. Elahe Izadi at The Washington Post points out that  “the handful of tweets that have Trevor Noah in the hot seat represent less than one percent of Noah’s entire Twitter output.” Comedians sometimes make bad jokes. If Noah stumbled into stereotypes on a few occasions—well, people make mistakes. Do we really need to make a big deal about it?

I certainly don’t think Noah should be fired. But I think it’s appropriate to criticize him for his public statements. Yes, it’s petty to call him out over a handful of tweets—but society, as a web of interpersonal relationships, norms, and small daily interactions, is, again, built around petty stuff. Women have their physical appearance policed, not through violence, but through offhand comments and shaming. When Noah writes, “'Oh yeah the weekend. People are gonna get drunk & think that I'm sexy!' - fat chicks everywherethat’s not just a joke. It's part of a system of norms that says that guys have a right to comment on women’s bodies and to sneer at them for being insufficiently sexual, or too sexual, or unattractive, or too attractive, or for expressing sexual desire, or for not expressing sexual desire.

The joke, in other words, is part of an etiquette, or ties into an etiquette, whereby women in public are supposed to feel ashamed for being women. Discrimination, stigma, and sexism—like segregation—function through small-bore norms, which determine what you can wear, or think, or feel, without being jostled, censured, or shamed.

And if prejudice is a norm, then ending prejudice has to involve etiquette as well. Should women feel shame for existing? Or should people feel shame for spouting sexist garbage? The answer is governed by etiquette—by what behaviors and what kinds of language are seen as publicly natural or acceptable. Noah is soon going to have a massive national platform. Is it okay for him to use that platform to sneer at women and Jews? Many are currently insisting, as a matter of etiquette, that it is not.

You might argue that this is superfluous; that everyone knows that it is not okay to insult Jews or women. But in fact, social norms change quickly and are constantly contested. Part of the way you can tell that etiquette is important is that it’s such a battleground. The controversy around the new Indiana religious-freedom law is a good example.

There is some uncertainty about what the law actually does or does not allow; some say it will make it legal for businesses to discriminate against LGBT people, some say it will not. But it seems clear that the law served as a signal to voters and a wider public (including Governor Mike Pence's possible supporters in the Republican presidential race) that the state supports those who want to treat gay people unequally. The massive backlash, including threats of boycotts from business leaders, caught Indiana by surprise. Pence thought that current norms allowed for public statements in favor of anti-gay discrimination. He is learning that he was incorrect.

Again, the issue here is not necessarily a legal one, since the legal issues are murky. It's symbolic. But symbols matter—or, to put it another way, social signaling matters. Prejudice and discrimination are validated and enforced in no small part through interpersonal, intercommunal understandings of what behavior is acceptable and what behavior isn't. Ending prejudice and discrimination means changing those understandings. At one point, Jews and gay people were seen as unpleasant and ridiculous. Associating with them was shameful. Now, to some degree and at some times, at least, discrimination against those groups is itself deemed unpleasant, ridiculous, and shameful. Changing the world sometimes involves repealing unjust laws. Just as often, though, it happens by changing the small, petty interactions that make up our daily lives.