Author Salman Rushdie appears during the Mississippi Book Festival in Jackson, Miss., on Aug. 18, 2018. Rushdie, whose writing led to death threats, has been attacked on stage at an event in western New York. (Rogelio V. Solis, Associated Press/The Minnesota Star Tribune)

"Professor, why should we allow hate speech?"

Over the past few years, that's become the most common question students ask me. My reply is simple: Human beings have different understandings of hate, love and everything in between. Almost any statement can be perceived as offensive. So once we prohibit "hate speech," we won't be able to speak at all.

If you disagree, I have two words for you: Salman Rushdie.

Rushdie, who was seriously wounded by a knife-wielding assailant on Friday, is probably the most famous purveyor of hate speech in the world. To be clear, I don't find what he writes and says hateful. But many people — possibly, millions of people — do.

That's why Iranian leaders issued a fatwa against Rushdie — that is, a call for his death — after he published his 1988 novel "The Satanic Verses." It's why a half-dozen countries banned the book, which fictionalizes parts of the life of the prophet Muhammad. It's why the novel's Japanese translator was stabbed to death and why its Norwegian publisher was shot outside his home.

And it's probably why 24-year-old Hadi Matar of Fairview, N.J., took a bus to the Chautauqua Institution in upstate New York, where he allegedly stabbed Rushdie about 10 times. Police haven't confirmed Matar's motive, but many Iranians assumed that he was carrying out the fatwa, which earned him fervent praise in their newspapers.

In Tehran, meanwhile, a delivery person interviewed by the Associated Press said he was "happy to hear" about the attack. "This is the fate for anybody who insults sanctities," he added.

That's the cry of the censor in all times and places: A word or idea is insulting what is most sacred to us, so it's our duty to shut it down.

Witness the book bans suffusing American school districts right now, mostly targeted at material about sex and gender. Critics allege that these texts threaten students by depriving them of sexual innocence.

Or consider the spate of GOP-sponsored bills in state legislatures barring the teaching of critical race theory, the 1619 Project and other curricula that deal with racism in the United States.

Most of my students are liberal Democrats, so they're appalled by these measures. But they often support their own brand of censorship against hate, aimed at protecting America's minority groups rather than the nation writ large.

Starting in the 1980s, hundreds of colleges and universities promulgated codes to prohibit negative remarks about minorities. The most famous one was adopted by the University of Michigan, which barred "any behavior, verbal or physical, that stigmatizes or victimizes an individual on the basis of race, ethnicity, religion, sex, sexual orientation, (or) creed."

But once you have decided that some speech is too hateful to be expressed, you won't have a leg to stand on when they come after Rushdie — or anyone else.

That's why Rushdie has spent the past three decades demanding freedom for all speech. He wrote in support of the Charlie Hedbo cartoons of Muhammad after Islamic terrorists attacked the Paris magazine in 2015. And he has also stood foursquare against left-wing efforts at universities to restrict what we can say about race, gender and sexuality.

"It's a very dangerous path for people to take to use censorship as a way of defending minorities because it will backfire," Rushdie told a University of Virginia audience in 2016. "It always has."

If you support the censorship of hate speech, from any side of the political aisle, stop pretending you believe in Rushdie's cause.

Jonathan Zimmerman teaches education and history at the University of Pennsylvania. He is the author, with cartoonist Signe Wilkinson, of "Free Speech and Why You Should Give a Damn."