Reza Aslan in California. Charley Gallay/Getty Images for Turner CNN host Reza Aslan faced backlash on Saturday after calling President Donald Trump a "piece of s---" because of Trump's response to the terrorist attack in London that left seven dead and dozens wounded Saturday night.

In a tweet Saturday that was later deleted, the University of California at Riverside professor who hosts "Believer" on CNN quoted Trump's use of several terrorist incidents in the UK to justify his executive action banning entry to the US by people from several majority-Muslim nations.

"This piece of s--- is a not just an embarrassment to America and a stain on the presidency. He's an embarrassment to humankind," Aslan wrote.

The tweet immediately sparked outrage on the right.

—Gov. Mike Huckabee (@GovMikeHuckabee) June 4, 2017

Aslan deleted the tweet and apologized Sunday afternoon, saying he lost control after what he saw as Trump's "derogatory" response to the London attack.

CNN distanced itself from Aslan in a statement Sunday but applauded the host for apologizing.

"Reza Aslan is not a CNN employee, but does host a series on the network," a CNN representative said. "We are pleased that he has apologized for his tweets. That kind of discourse is never appropriate."

Aslan, who is Muslim, has been highly critical of Trump's travel ban, which was halted by a federal appeals court because it was seen as unconstitutionally singling out Muslims.

The professor went viral for his clash with Trump supporter Kayleigh McEnany last year over the proposed ban as well as Trump's claims that thousands of Muslims in New Jersey celebrated after the September 11, 2001, terrorist attacks, an unfounded assertion.

"Anti-Muslim bigotry has been the hallmark of Donald Trump's campaign throughout," Aslan said.

Trump's response to the incident on Twitter was criticized by many in the UK and on the left who have frequently blasted his occasionally misinformed attempts to blame violent incidents on Islamic extremists.

CNN has become a frequent target for Trump and the right as the network has ramped up its reporting on the Trump administration.

This was the second time this week a CNN-affiliated personality enraged the right.

CNN severed ties with comedian Kathy Griffin after she posed with a bloodied prop Trump head.

Though Griffin has a decades-long career in comedy and maintains minimal ties to the network — she has hosted its New Year's Eve special — some on the right labeled her a "CNN star."