Fox News, television’s equivalent of a presidential safe space, kept up its steadfast defense of President Trump even as he faced an uproar this week over his response to the violence at a white supremacist rally in Virginia last Saturday. Anchors like Sean Hannity and Tucker Carlson praised the president and lauded his bare-knuckle criticism of the news media.

But notably, some pundits broke ranks. Eboni K. Williams, a host of the 5 p.m. show “The Specialists,” derided Mr. Trump in exceptionally blunt terms, calling his initial remarks about the rally “cowardly and dangerous” and accusing the president of minimizing “blatant, flagrant hatred” rather than risk roiling a portion of his base.

It was the kind of unvarnished criticism that Fox News usually outsources to liberal guests — and Ms. Williams, who is African-American, said that her words had come with a price.

In the days since her segment aired, Ms. Williams said she had received nearly 150 menacing messages from people who denounced her remarks and called her a traitor, a racist, a “disgrace,” and anti-American. Some of the messages, she said, implied an intent to harm, and she said she requested and received a security escort from Fox News.

“I’ve been on Fox News on and off for five years now,” Ms. Williams, 33, who calls herself politically moderate, said in an interview on Wednesday. “Never in my life had I received the response that I received.”

Ms. Williams is not registered in any political party, and she said last year that she did not vote for Mr. Trump or Hillary Clinton for president. She said she had felt compelled to air her indignation with Mr. Trump in part because she believed her audience deserved a diversity of viewpoints.

“I felt utterly compelled in that moment, particularly as a black woman who works on Fox News Channel, and has the privilege and a responsibility to address an audience that otherwise doesn’t necessarily get my point of view, or the point of view of people like me,” she said. “They probably don’t see much of any of the diverse point of view that I can offer.”

Not every viewer has been pleased. “I couldn’t get to the remote soon enough” to change the channel, one Twitter user wrote on Wednesday, after Ms. Williams again criticized Mr. Trump on the air. Another wrote: “I wonder if @FoxNews now regrets the divisive hateful words spewed out of the nasty mouth” of Ms. Williams.

Mr. Hannity and other anchors, including the morning show hosts on “Fox & Friends,” rarely question the president, and several of them recently dined with Mr. Trump at the White House. Rupert Murdoch, Fox News’s executive chairman, is a regular adviser to Mr. Trump, even counseling him on the fate of Stephen K. Bannon, the president’s chief strategist.

But Mr. Trump has his critics on Fox News. Juan Williams regularly battles with his pro-Trump co-hosts on the prime-time show “The Five.” The daytime news anchor Shepard Smith can offer up tough criticism. “So far we’ve been unable to find the very fine people protesting with the white supremacists,” he said sarcastically on Wednesday’s broadcast, referring to Mr. Trump’s assertion that “very fine people” were among the demonstrators in Charlottesville.

Ms. Williams’s criticism was more scathing. Addressing Mr. Trump directly on the air Monday, she said: “While you personally may not be a racist, President Trump, what you are is all too happy to reap the benefits of their support, and you even tacitly encourage them with evasive, irresponsible statements.”

Ms. Williams, a lawyer who formerly worked at CBS News, said in the interview Wednesday that her superiors at Fox News had not expressed concern.

“I’ll tell you the truth, if they had said anything, it would have shocked me,” she said. “I’m no puppet for the network. I call Fox as I see Fox. And for me it’s been a positive experience. It’s not been a perfect experience, but I’m there because the good outweighs the bad.”

Her “Specialists” co-host, the libertarian commentator Kat Timpf, has also drawn attention for criticizing Mr. Trump on the air, calling his news conference “one of the biggest messes that I’ve ever seen.”

“The Specialists” usually features the anchor Eric Bolling, who was suspended this month after HuffPost reported on accusations that he had sent lewd messages to co-workers. (Mr. Bolling has denied wrongdoing.) Ms. Williams acknowledged that his absence had created some uncertainty. “The future of our show hangs in the balance,” she said.

Rumors have circulated that Fox News might reshuffle its schedule, adding Laura Ingraham in prime time and moving “The Five” from 9 p.m. to 5 p.m., when “The Specialists” now airs. Asked about the speculation, Ms. Williams said, “Your guess would literally be quite as good as mine.”

She added: “We have no idea. They’ve not told us or any of the other co-hosts or producers anything other than they believe in this show.”