He used the word during Friday’s Real Time.

Real Time host Bill Maher, who is very much white, on Friday crossed one of those lines that should never be crossed: He dropped the n-word on live television.

Maher used the word during an interview with Nebraska Sen. Ben Sasse (R). Here’s how it went, courtesy of the Root:

MAHER: Adults dress up for Halloween, they don’t do that in Nebraska? SASSE: It’s frowned upon. We don’t do that quite as much. MAHER: I gotta get to Nebraska more. SASSE: You’re welcome. We’d love to have you work in the fields with us. MAHER: Work in the fields? Senator, I’m a house ni**er.

At that moment, Sasse suddenly quieted down. The crowd responded with a mix of laughter and groans. Maher then claimed his statement was “a joke” — to applause from the audience.

Many people have already reacted strongly to the moment on social media, mocking Maher and calling for HBO, which airs Real Time, to fire him.

Sasse later commented in a series of tweets. “I’m a 1st Amendment absolutist. Comedians get latitude to cross hard lines,” he wrote. “But free speech comes with a responsibility to speak up when folks use that word. Me just cringing last night wasn’t good enough.” He added, “Here’s what I wish I’d been quick enough to say in the moment: ‘Hold up, why would you think it’s OK to use that word? … The history of the n-word is an attack on universal human dignity. It’s therefore an attack on the American Creed. Don’t use it.’”

In a statement to the Hollywood Reporter, HBO also criticized Maher’s use of the word. “Bill Maher’s comment last night was completely inexcusable and tasteless,” the network’s statement said. “We are removing his deeply offensive comment from any subsequent airings of the show.”

It’s unclear if HBO will take further action against Maher.