PHOENIX — More than 16 million people, many of whom are foreign, passed through the Tom Bradley International Terminal at Los Angeles International Airport in 2017. Most days, they only have to deal with immigration and customs inspectors. But one day last June, they dealt with a small, vocal group of protesters holding signs decrying Islam.

They weren’t targeting their message to lawmakers or activists. Instead, they targeted foreigners — particularly Muslims — who had finished long intercontinental flights from far-flung places.

Was this demonstration a legitimate act of political speech? Was it hate speech?

Many people struggle with the boundary between offensive protest speech and hate speech.

“It is a matter of what the target perceives it to be,” said Phyllis B. Gerstenfeld, a hate crimes expert at California State University, Stanislaus. “One way of thinking about it is, what is the primary intent of the speaker. Is it to affect change or is to harm someone psychologically or verbally?”

Jared Taylor of Oakton, Virginia, who founded a self-described “white advocacy” group that is best known for its “American Renaissance” magazine and website, said that threshold is too low.

“What is hate speech? It’s defined basically as anything that upsets someone,” he said. “Certain facts will offend people. Certain opinions will offend people. If you run your life strictly on the basis on who you might offend, how far are you going to get?”

In 1968, the U.S. Supreme Court weighed in. In Brandenburg v. Ohio, justices ruled that speech isn’t protected if it incites violence. They devised the “imminent lawless action” test: speech must advocate violence and be likely to incite it.

“Incitement” is in the eye of the beholder, especially in today’s heated political climate, free speech experts say.

Some social justice activists and scholars consider upsetting words a form of violence or incitement toward violence, especially with how fast word can spread on the internet, said Benjamin Krueger, who teaches political rhetoric and discourse at Northern Arizona University.

Che Rose of Washington, D.C., is one of those social justice advocates. An expert in online and alt-right “gamer” culture, he said offensive speech might not be immediately harmful, but it makes people think violence toward certain groups is acceptable.

“If people know it’s OK to say something, then they think it’s OK to do it,” Rose said. “They’re pushing norms in a bad direction.”

Taylor disagreed. He said the entire concept of free speech is to protect the right to be controversial, and to offend people.

“We can’t simply decide ‘OK, we have everything figured out, and anything that deviates from what we’ve got figured out is wrong is shut out,’” Taylor said. “That’s the end of progress. That’s the end of any kind of free debate, that’s the end of democracy, that’s the end of the United States, as far as I’m concerned.”

Equating words with violence creates “philosophical problems,” Krueger said, explaining that laws regulating words are content-based restrictions, and are rife with legal complications.

So, those protesters at the airport? Some experts say their message was hateful, but others claim it was a way to bring attention to a controversial cause. Based on the law, it is protected.

But Rose said people who preach hate will be judged through the lens of history.

“When they make the movies about this decade, you’re the bad guy,” he said of the perpetrators of hate.