The husband of a woman photographed giving the Nazi salute outside a Trump rally said it was done as a "teaching moment" for protesters comparing Trump to Adolf Hitler.

Chicago Tribune via Getty Images Donald Trump supporter Birgitt Peterson of Yorkville, Ill., argues with protesters outside the UIC Pavilion after the cancelled rally for the Republican presidential candidate in Chicago on Friday, March 11, 2016. (E. Jason Wambsgans/Chicago Tribune/TNS via Getty Images)

On Friday night, Trump supporters and protesters clashed in Chicago, leading to the cancellation of a rally for the Republican candidate. Don Peterson and his wife, Birgitt Peterson, were leaving the University of Illinois pavilion when they said protesters began to hurl insults at them.

"They were calling us names like 'skinheads' and 'Nazis' and stuff like that," Don Peterson, 70, said. "There was a girl holding a sign that said Hitler equals Trump, so we went up to her and said 'That is really stupid.'"

And when protesters held up fists and chanted "Bernie," Birgitt -- who was born in West Berlin in 1946 -- said the gestures reminded her of the Nazi salute, according to her husband.

"They did their version of the Nazi salute and called us Nazis," Peterson said. He and his wife responded to the protesters: "'If you’re gonna do it, do it right, here’s the right way to do the Nazi salute.'"

And that's when Birgitt Peterson raised her arm, captured in a now viral image by Chicago Tribune photographer E. Jason Wambsgans.

"My wife was responding to them and making this a teaching moment," Mr. Peterson said. "I'm all for their right and support them for protesting, but you don’t call people Nazis, or say Trump or people who support him are the equivalent of Nazis -- that is asinine. That is ridiculousness."

"If they're going to make the comparison, they ought to at least know what the Nazi salute was and what it meant," he went on. "If you're gonna bastardize history, at least know the history you're bastardizing."

The Petersons said they've gotten several threatening phone calls since the photo was published.

"We aren't Nazis," Don Peterson said. "Let me assure you, we are not, never have been, never will be, part of an organization like that. The Republican and tea party are the only two parties we’ve been a part of. Some people compare it to Nazis -- it's not in my mind."