Maher used the slur in an exchange with Sen. Ben Sasse, R-Nebraska, who appeared on the program Friday night to promote his book. Sasse kept quiet following the late-night comedian's remark, which was in the context of a joke and not censored when it initially aired on HBO.
Sen. Tim Scott, R-South Carolina, who is black, lamented "double standards"
Saturday morning on Twitter and elaborated on his comments at the Iowa "Roast and Ride."
"Too often, too many people give the liberals a break on incendiary remarks that they make and it's time to hold their feet to the fire and it's good news to see people come out now and do so. It's necessary," Scott told an audience of reporters. He declined to comment on whether Maher should be fired.
Asked to elaborate on his "double standards" remark, Scott's office said the senator "has been vocal about the racially-charged comments he himself has received from the so-called tolerant left. His tweet this morning was in reference to an extremely inappropriate and offensive term used by a liberal commentator on national television."
Rep. Yvette Clarke, a New York Democrat, called Maher's remark "completely unacceptable."
Democratic Rep. Ted Lieu of California also slammed the remark.
"I believe that Bill Maher's comment was inexcusable and inappropriate and he should not have said it and I'm pleased he has apologized for making that remark," he told CNN's Ana Cabrera.
Sasse also took to Twitter Saturday morning to address his lack of response at the time of the incident. Sasse wrote that while he believes as "a 1st Amendment absolutist" it is Maher's right "to cross hard lines," though he should have spoken up.
"Free speech comes with a responsibility to speak up when folks use that word. Me just cringing last night wasn't good enough," Sasse wrote. He added that he wished he had been "quick enough" to tell Maher that "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."
Following these reactions, Maher issued an apology on Saturday afternoon.
"Friday nights are always my worst night of sleep because I'm up reflecting on the things I should or shouldn't have said on my live show," Maher said in a statement. "Last night was a particularly long night as I regret the word I used in the banter of a live moment. The word was offensive and I regret saying it and am very sorry."
HBO also condemned Maher's use of the racial epithet.
"Bill Maher's comment last night was completely inexcusable and tasteless," Quentin Schaffer, executive vice president for corporate communications at HBO, said in a statement. "We are removing his deeply offensive comment from any subsequent airings of the show."
This is not the first time Maher has come under fire. He has created controversy for his views on religion, particularly Islam, and lost his ABC show, "Politically Incorrect," after remarks he made in the wake of the September 11 attacks.