Donald Trump’s tetchy relationship with protesters took another controversial turn on Sunday when he appeared to mock a turban-clad man ejected from a campaign rally in Iowa.

The incident began as Trump was inveighing against “radical Islamic terror,” a common theme in his stump speeches.

“Somebody has to say what’s going on,” he said roughly 15 minutes into an hour-long speech at Muscatine High School, before referencing the Sept. 11, 2001, attacks and the San Bernardino, Calif., shooting in December.

“When planes fly into the World Trade Center, and into the Pentagon, and wherever the third plane was going, when people are shooting their friends in California–” Trump said before abruptly pausing as his attention was drawn to the gym’s upper level, where a security guard and a police officer were confronting two protesters.

The protesters were trying to unveil a white sheet with the words “stop hate.” One of the protesters wore a beard and bright-red turban similar to those worn by Sikhs.

“Bye, bye,” Trump said sarcastically as the guard pushed the protester toward the exit and as the crowd began whistling. “Goodbye, goodbye.”

The capacity crowd then broke into chants of “U.S.A., U.S.A.,” before Trump appeared to make a quip about the protester’s turban, which was roughly the same color as Trump’s popular red “Make America Great Again” hats.

“He wasn’t wearing one of those hats was he?” Trump said, gesturing to a supporter’s hat and eliciting a laugh from the crowd.

“And he never will,” Trump continued, segueing back into his speech, “and that’s okay, because we got to do something folks because it’s not working.”

The barbed quip was just the latest in a string of heated interactions between Trump, his supporters and protesters.

[50 years later, disagreements over young Trump’s military academy record]

The incidents began in October, when Trump was repeatedly interrupted by protesters during a raucous Miami rally.

“See, the first group, I was nice. Oh, take your time,” he said at the time. “The second group, I was pretty nice. The third group, I’ll be a little more violent. And the fourth group, I’ll say get the hell out of here!”

A month later, Trump did, in fact, appear to take a harsher stance toward his hecklers.

When a Black Lives Matter protester interrupted his speech in Birmingham, Ala., on Nov. 21, Trump told security: “Get him the hell out of here, will you, please? Get him out of here. Throw him out!”

A video captured by CNN appeared to show a group of white men surrounding and attacking the African American protester. A Washington Post reporter in the crowd watched as one of the men put his hands on the protester’s neck and heard a female onlooker repeatedly shout: “Don’t choke him!”

When asked the next morning about the rough treatment of the protester, Trump replied: “Maybe he should have been roughed up, because it was absolutely disgusting what he was doing.

“I have a lot of fans, and they were not happy about it,” he said on Fox News. “And this was a very obnoxious guy who was a troublemaker who was looking to make trouble.”

[Trump on rally protester: ‘Maybe he should have been roughed up’]

Since then, the confrontations between Trump, his supporters and protesters have kept coming. Cries of “Dump Trump” interrupt many of the Republican presidential hopeful’s events, only to be drowned out by chants of “Trump, Trump, Trump,” his campaign’s way of alerting security to troublemakers in the crowd.

Several incidents earlier this month, however, have called into question once again whether Trump’s protesters are treated fairly. In Lowell, Mass., two protesters silently holding up signs that said, “America is already great” and “God, bless Obama!” were threatened by Trump supporters, before their signs were destroyed.

“Do you think I should hurt you right now?” one Trump supporter asked the protesters. “You don’t belong here. Go away. Shut up, shut your mouth.”

“Ditch those,” another man said, gesturing to the protest signs. “Ditch ’em.”

The two Trump supporters then snatched at the signs, tearing them to pieces. Yet it was the protesters who were escorted out of the event.

A few days later, another peaceful protester was ejected from an event in Rock Hill, S.C. The woman, a 56-year-old Muslim flight attendant named Rose Hamid, stood silently wearing a white hijab, a blue T-shirt reading, “Salam, I come in peace,” and a yellow eight-pointed star — reminiscent of the six-pointed stars Jews were forced by the Nazis to wear on their clothing during the Holocaust — with the message “Stop Islamophobia.”

[Muslim woman gets kicked out of Trump rally — for protesting silently]

Although Hamid didn’t make a scene, the crowd erupted in chants of “Trump! Trump! Trump!” and security quickly escorted her out. She later told CNN that she attended the rally because “most Trump supporters probably never met a Muslim.

“This demonstrates how when you start dehumanizing the other, it can turn people into very hateful, ugly people,” Hamid added. “It needs to be known.”

Beginning in December, the Trump campaign began telling crowds that no protesting of any sort is allowed and that protesters needed to stay in a free-speech space outside the venue, The Post’s Jenna Johnson reported. The announcement, which airs before events, also asks supporters to “not harm a protester” but rather to wave signs and chant “Trump, Trump, Trump,” to alert security.

[Trump campaign devises a new strategy for identifying and removing protesters]

Although feisty confrontations with protesters are nothing new for Trump, Sunday’s speech began on an unusual note.

Trump said he had just come from church.

“What a day,” he began. “I just got back from church and it was good, it was really good. I learned something. We talked about humility at church today.

“I don’t know if that was aimed at me,” he said to laughs. “Perhaps. I don’t think the church knew that I was coming so maybe it was just by luck, but we talked about humility.”

Trump then said it was “crunch time” in Iowa with a week left before the state holds its Feb. 1 caucuses, the first opportunity of the 2016 cycle for voters formally to express their preference for a nominee in each party.

[Poll: Trump gains 15 points on Cruz in Iowa in two weeks]

“Look at all these beautiful hats,” Trump said, pointing to the crowd. “We’re going to follow what it says — look at that — we’re going to make America great again.”

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