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Not impressed. Sen. Bernie Sanders and Russell Simmons are up in arms over Donald Trump's anti-Muslim stance, and they're both making sure the presidential hopeful knows what they think of him.

Appearing on The Tonight Show Starring Jimmy Fallon on Tuesday, Dec. 8, presidential candidate Sanders blasted the real estate mogul's views, calling them "crap" and insisting the American public was not going to stand for it.

"Throughout history we’ve had the demagogues trying to divert attention away from the real issues," Sanders, 74, said. “What somebody like Trump is trying to do is to divide us up. A few months ago we were supposed to hate Mexicans, and he thinks they are all criminals and rapists. And now we are supposed to hate Muslims, and that kind of crap is not going to work in the United States of America," he continued, to much audience applause.

Someone else unimpressed by Trump's emotive views is Def Jam Records co-founder Simmons, who considers himself a pal of Trump's and has stayed in his home on multiple occasions.

Writing an open letter to the Republican front-runner, urging him to stop the "bulls--t," Simmons, 58, begged his former friend to be true to his real self.

"Over 30 plus years you have been an amazing friend; endorsing my books, coming to my shows, flying me on your planes, your helicopters, and even allowing my family members and myself to stay in your house in Florida many times," Simmons writes in his message to Trump. "So, it kinda pains me to know that my public statements about your candidacy have strained or ruined our friendship. However, the fact is, what’s at stake is bigger than us."

"My friends, both Muslims and Jews, are saying there are so many comparisons between your rap and Hitler’s, and I cannot disagree with them, Donald," Simmons went on. "You can’t possibly want your kids or your wife Melania (all of whom I know and respect) to live with that. You are a born leader, who is set to possibly win the nomination of your party, but don’t compromise what I know is in your heart to do it. You are a generous, kind man who has built a career on negotiating deals where everybody wins. Now, you seem like a one-man wrecking ball willing to destroy our nation’s foundation of freedom," he went on.

Sanders' and Simmons' distaste for Trump's words stems from an email Trump sent to reporters, suggesting that all Muslims be barred from entering U.S. borders.

The blond-haired politico called for a "total and complete shutdown of Muslims entering the United States" following several terrorist-related attacks in San Bernardino, Calif., and France. "Where this hatred comes from and why we will have to determine. Until we are able to determine and understand this problem and the dangerous threat it poses, our country cannot be the victims of horrendous attacks by people that believe only in Jihad, and have no sense of reason or respect for human life," he wrote.

During a phone-in interview with Joe Scarborough on MSNBC's Morning Joe on Tuesday, Dec. 8, Trump stood by his comments.

“I’m using common sense,” Trump, 69, who called in to the show, said. “I spoke in front of thousands of people last night. Your reporters are reporting it. It was the biggest crowd they’ve ever had on the [ship the USS] Yorktown," he insisted, evidently unrepentant.

He then embarked on a non-stop monologue that led to Scarborough cutting the GOP candidate off mid-flow to go to break.

Watch Sanders and Jimmy Fallon discuss Trump’s divisive words in the video above.

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