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HBO "Real Time" host Bill Maher defended himself Friday night after critics spent part of the week equating his past jokes -- likening President Donald Trump to an orangutan -- to Roseanne Barr's Twitter post about a former adviser to President Barack Obama.

Many of the critics called for HBO to fire Maher, just as ABC fired Barr despite this year's success of her rebooted "Roseanne" comedy series.

During his opening monologue, Maher said four “key facts” made his ape jokes different than Barr’s tweet, in which Barr had referred to Valerie Jarrett, a black woman and former Obama top aide, using an allusion to the "Planet of the Apes" movies.

“One, Trump is an orangutan,” Maher said. “Two, white people have not been subjected to a racist trope comparing them to apes for hundreds of years.”

Maher’s third explanation was that his joke was a response to Trump’s 2013 accusations that President Obama was not born in America and called for the release of the president’s birth certificate.

“And four, I’ve already been fired by ABC,” Maher said, referring to his "Politically Incorrect" program, which aired from 1993 to 2002.

Some of Maher's critics contend he has been able to keep his HBO show on the air because he is a liberal, while Roseanne, “a free-thinking Trump supporter,” was fired.

“Wait, Bill Maher makes comparisons to Trump being a gorilla all the time,” tweeted conservative activist Charlie Kirk, director of Turning Point USA, a nonprofit that says it tries to educate students on "true free-market values."

Maher's comments "get classified as ‘jokes’ by the media and he is of course allowed to keep his show and not have his life ruined,” Kirk said.

But Maher himself is familiar with getting into hot water for inappropriate comments.

ABC canceled Maher’s “Politically Incorrect” in 2002 following comments he made about the Sept. 11, 2001, terror attacks. The comedian argued that “the labeling of terrorists as cowards was hypocritical, and that we [the U.S.] have been the cowards, lobbing cruise missiles from 2,000 miles away,” Bustle reported.

In an incident last year, Maher apologized after he was criticized for calling himself a “house n----r” on his HBO show. The network later removed his comment from future airings of the episode, calling it “inexcusable.”

Fox News’ Kathleen Joyce contributed to this report.