The tang of fall is nearly in the air. The summer is all but over. Football season is here. Are you ready for some . . . culture war?

This war may feel unending, but it only began a little more than two years ago. During a preseason game on Aug. 26, 2016, Colin Kaepernick, then the quarterback of my beloved San Francisco 49ers, refused to stand during the playing of the national anthem to protest police brutality against African-Americans. Soon the trend spread across the NFL.

President Donald Trump, who is to rabble-rousing what Tom Brady is to passing, sensed an opening. In an interview with “Fox & Friends,” he denounced the protesting players for showing “a lack of respect for our country” and suggested “they should try [moving to] another country.”

A year later, at a rally in Alabama on Sept. 22, 2017, he said, “Wouldn’t you love to see one of our NFL owners when someone disrespects our flag to say, ‘Get that son of a bitch off the field right now . . . he’s fired!'”

Two days later, he tweeted: “Standing with locked arms is good, kneeling is not acceptable. Bad ratings!”

Last October, Vice President Mike Pence even attended an Indianapolis Colts-49ers game just so he could walk out in disgust after seeing 49ers players kneel. In July, Trump escalated by suggesting that players should be ejected from a game the first time they kneel and “out for season/no pay” the second time.

Kaepernick has not played an NFL game since January 2017, even though he is good enough to be a backup QB and perhaps even a starter. He has filed a grievance charging that NFL owners colluded against him.

Under pressure from Trump, the NFL owners briefly adopted a policy in May of fining players who refused to stand during “The Star-Spangled Banner.” That policy was retracted as soon as it was leaked. But, despite the lack of a formal league position, on Sunday only two players knelt while a few others raised their fists.

Naturally Trump felt compelled to weigh in with a tweet: “Wow, NFL first game ratings are way down over an already really bad last year comparison. Viewership declined 13%, the lowest in over a decade. If the players stood proudly for our Flag and Anthem, and it is all shown on broadcast, maybe ratings could come back? Otherwise worse!”

Kaepernick struck back in a Nike advertising campaign with the tag line: “Believe in something. Even if it means sacrificing everything.”

The cynicism from both the president and the shoe company is stunning. Trump, the kind of scoundrel who Samuel Johnson warned us about, is taking advantage of the protests to appeal to flag-waving supporters, many of whom also nurse racist resentment against highly paid African-American athletes. Nike, for its part, is taking advantage of the protests to sell its products – apparently successfully.

My own sympathies have swung back and forth, as if this were a close football game. Initially I was critical of Kaepernick. I cited the words of retired Navy Adm. William McRaven, who wrote: “Those that believe the flag represents oppression should remember all the Americans who fought to eliminate bigotry, racism, sexism, imperialism, communism, and terrorism.”

I argued that Kaepernick’s protests were disrespectful to all the soldiers who defended American freedom – and they ignored the fact that, although America remained racist and imperfect, “it has made tremendous progress during its history.”

But as Trump continued savaging the protesting players, my sympathies swung in their direction – and there they have remained. The issue is no longer whether it’s appropriate to protest “The Star-Spangled Banner.” The issue now is whether a demagogue will succeed in stifling protests and pandering to racist yahoos.

Trump’s attacks on the NFL players are only a small part of his larger war on dissent. He has suggested that people who exercise their First Amendment rights to burn flags should be jailed or lose their citizenship. He has repeatedly saidlibel laws should be loosened to punish the press, which, echoing dictators, he calls the “enemy of the American people.” In response to protests during last week’s confirmation hearings for Supreme Court nominee Brett Kavanaugh, Trump said, “I don’t know why they don’t take care of a situation like that. I think it’s embarrassing for the country to allow protestors.”

Embarrassing? Protests are the very essence of America! It is a country founded in protest. (Remember the Boston Tea Party?) Protests, such as those in favor of labor rights, women’s suffrage, civil rights and gay rights, helped to make America as great as it is. You don’t have to agree with protesters – and I have disagreed with plenty, from the nuclear freeze movement in the 1980s to Occupy Wall Street more recently – to recognize that they are exercising a sacrosanct, constitutional right “to assemble, and to petition the government for a redress of grievances.”

It is, in fact, precisely to defend the right to free speech that countless patriots have given the last full measure of devotion. That the president doesn’t understand that protest is as American as watching football on fall Sundays is far more disturbing than anything that any NFL player could possibly do during the anthem.

Max Boot, a Post columnist, is the Jeane J. Kirkpatrick senior fellow for national security studies at the Council on Foreign Relations and a global affairs analyst for CNN. He is the author of the forthcoming “The Corrosion of Conservatism: Why I Left the Right.”

Miami Dolphins wide receiver Kenny Stills (10) and Miami Dolphins wide receiver Albert Wilson (15) kneel during the national anthem before an NFL football game against the Tennessee Titans, Sunday, Sept. 9, 2018, in Miami Gardens, Fla. (AP Photo/Wilfredo Lee)