When does free speech become hate speech?

Anti-Islam speakers have been making the rounds in northern Minnesota and around the country, warning crowds about refugees and calling on them to oppose Muslims where they live.

They include John Guandolo, a former FBI agent who's a fixture in anti-Islam circles. MPR News' John Enger reported on Guandolo's recent speech at a Warroad, Minn., church.

"Are you prepared?" Guandolo called out. "Are you prepared for the two or three dozen jihadis in, pick a city in Minnesota, with mortars or shoulder-fired rockets? You don't think they can get those in the United States?"

Some people consider this type of rhetoric to be hate speech. But it's not illegal, said Richard Cohen, the president of the Southern Poverty Law Center.

"If it were, there would be many, many people in jail," Cohen said. "What you can't do is cross the line between hate speech and incitement."

The courts have narrowly defined incitement as expression that pushes "imminent lawless action," he said. Anything short of that definition is protected speech under the First Amendment.

But just because hateful rhetoric is legal, doesn't mean it can't be dangerous, Cohen added. "You can plant the seeds of violence in people, you can rile up a crowd, and violence sometimes follows."

From a common-sense standpoint, hate speech is defined as expressions that vilify groups of people because of their religion, race, ethnicity or other factors, Cohen said.

In disparaging entire religions, like the anti-Islam speakers, for example, Cohen said certain speech can actually increase the chance of terrorism.

"You play into this idea that we're at war with a particular religion," he said, "and frankly that's the message that ISIS and al-Qaida want to make."

For Cohen's full interview with All Things Considered host Tom Crann, use the audio player above.