In the small, homogeneous town where I grew up, before the word “diversity” was in common use to refer to people different from each other in some way, it was pretty common to hear racial and religious slurs.

My dad, born in 1919 and whose longest time out of Nebraska was serving in the still-segregated Army at Fort Riley, Kansas, would refer to black athletes as “boy,” a term that harkens back to slavery and segregation. Others used even more offensive terms.

Not many black people lived in Beatrice, Nebraska, other than the Scott brothers, barbers just down the street from my house. Beatrice didn’t have a synagogue or a mosque or hardly any residents who weren’t as white as our yards in January.

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Beatrice had a Catholic school, and I remember hearing terms that I didn’t even understand, but later grasped as derisive toward Catholics.

Back then, towns like Beatrice and Glenwood Springs were more isolated from outside influences than in today’s high-tech, hyperconneted world. The struggle for civil rights was more theoretical to us than real.

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So by the time we reached middle school, most of my classmates and I had grown up hearing things, and some of us saying things, that were just plain bigoted.

This is a rationalization for bad behavior, but I think most of the slurs were rooted more in unchallenged ignorance more than in hate. If someone started telling racist jokes and we’d heard adult relatives do similar things, we would join in or laugh along. It was adolescent mob mentality.

Our teachers helped us learn the issues of the world and why not to say things that demean groups of people. Seventh-grade social studies included a unit on stereotypes, the first time I’d heard the term.

For the most part during my adult life, these things we learned in middle school have been a standard of expected conduct in our increasingly diverse society. Overall, Americans gradually got better about how we talk about people who aren’t like us.

It’s not just a question of being polite. If we have to think about how we describe someone or how we address someone, we are breaking the ignorance and disregard of a less sophisticated time in our history. Over time, what we say and what we hear changes how we think.

Racist, sexist, homophobic, religiously biased language was marginalized. Some people still thought these things but for the most part knew not to say them — though Barack Obama’s election showed us that the proportion of our population with racist feelings is larger than many of us imagined.

Then came Donald Trump’s presidential campaign. In many ways, Trump is like the name-calling bullies who got in trouble with my middle-school teachers — but there’s no one to send a 70-year-old self-proclaimed billionaire to detention.

Trump, with his cruel language toward Mexicans, his sweeping generalizations about Muslims, his racial dog whistles that we all can hear, has emboldened those so inclined to start saying the things they learned as children just aren’t appropriate.

Video from his rallies captures grown-up mob mentality, with supporters shouting the n word, calling protesters fags, calling Hillary Clinton a bitch who should be hanged and making references to her body — which, oddly enough, no one did with John McCain, Mitt Romney or Barack Obama.

It’s spreading into everyday life, across the country.

A Latina restaurant worker in Virginia who is a citizen recently found a note on a receipt that said, “We only tip citizens.”

In Iowa and Indiana, students taunted opposing Latino basketball players last winter with chants of “build a wall,” and “Trump.”

An El Salvadoran man was dragged from his car and beaten last year at the El Jebel City Market by man who yelled obscenities about our president and that “Mexicans” should go home.

Words matter. Trump launched his campaign two months before the El Jebel beating by saying of Mexican immigrants, “They’re bringing drugs. They’re bringing crime. They’re rapists.” Then he got serious about putting people down.

As much as any other aspect of his rise, this is the threat of a Trump presidency — that we will regress and become a more hateful society.

Even if he loses, he has ripped at our social fabric in a way that frays decades of gains against discrimination and stereotyping.

The makeup of America is changing in a way that cannot be stopped. We will either embrace our growing diversity or risk being more deeply divided by it.

Racism and hatred are driven by fear. Fear’s running mate is ignorance. Its antidote is familiarity, in this case, getting to know people who seem different from us and learning how much like us they are.

This doesn’t just involve people of different religions and skin colors. America is so polarized today that liberals and conservatives need to reach out to each other.

In this process, we will learn that we are more alike than different. A conservative columnist and I recently exchanged emails in which we agreed that we make each other think harder, which we both enjoy.

Whichever way the election goes, America desperately needs to think harder and choose our words responsibly.

It will help us remember our middle school lessons and to behave like grown-ups.

Randy Essex is publisher and editor of the Post Independent.