For all the Republicans who have chalked up President Donald Trump’s outbursts over the past few weeks to just Trump being Trump, Sen. Cory Booker (D-NJ) had a very different message at a Senate Judiciary Committee hearing on Tuesday: The president’s words matter.

The latest controversy embroiling the White House came after an immigration meeting between the administration and key lawmakers, in which Trump reportedly called Haiti and African nations “shithole countries” and questioned why their residents were coming to the United States. Senators of both parties who were present at the meeting, including Sens. Dick Durbin (D-IL) and Lindsey Graham (R-SC), confirmed that Trump used the phrase.

Booker and other senators got their chance to question Homeland Security Secretary Kirstjen Nielsen about the meeting during a Senate Judiciary Committee hearing on Tuesday, and they took it.

Earlier during her sworn testimony in front of the committee, Nielsen disputed that Trump had used the term “shithole” during the meeting, instead characterizing his speech as “impassioned.” While she admitted the president had used “tough language,” she said others in the room had done the same.

Booker did not find Nielsen’s story persuasive.

Pounding his fists on the Senate dais as he spoke, the senator told Nielsen that he was “seething with anger” over Trump’s recent comments disparaging black people from foreign nations.

Pointing to racially charged violence in America including last summer’s deadly protests in Charlottesville, Virginia, Booker pointedly told Nielsen that Trump’s words — followed by denials from White House that he said them — were dangerous.

“The commander in chief, in an Oval Office meeting, referring to people from African countries and Haitians with the most violent, vulgar language,” Booker said. “When ignorance and bigotry is allied with power, it is a dangerous force in our country. Your silence and your amnesia is complicity.”

Sen. Booker to DHS Sec. Nielsen, who was in White House immigration meeting: "When ignorance and bigotry is allied with power, it is a dangerous force in our country. Your silence and your amnesia is complicity." pic.twitter.com/eR4zAsE2jF — NBC News (@NBCNews) January 16, 2018

White House officials aren’t the only ones disputing whether Trump used the term “shithole”; two Republican lawmakers who attended last week’s immigration meeting, Sens. Tom Cotton (R-AR) and David Perdue (R-GA), released a statement on Friday saying they did not recall Trump making the remark.

But fellow Republican Lindsey Graham has not. Instead, he doubled down on his version of the story, telling reporters, “My memory hasn’t evolved. I know what was said and I know what I said.”

Booker applauded Graham for speaking out about Trump’s comments.

“From Dick Durbin to Lindsey Graham, they seem to have a much better recollection of what went on,” he told Nielsen. “You’re under oath — you and others in that room that suddenly cannot remember.”

Booker continued:

I’ve been in the Oval Office many times, and when the commander in chief speaks, I listened. I don’t have amnesia on conversations I’ve had in the Oval Office going back months and months and months. When Oval Office rhetoric sounds like social engineering, we know from human history the dangers of that. Our greatest heroes in this country spoke out about people who have convenient amnesia or who are bystanders. Martin Luther King said, “A man dies when he refuses to take a stand.”

Booker and Sen. Kamala Harris (D-CA), who, like Booker, is African American, both said they were concerned that Trump and other White House officials are stoking racial tensions in America and not doing enough to combat the threat of white supremacy.

Between 2001 and 2015, more Americans were killed by homegrown right-wing extremists than by Islamist terrorists, according to a study by the nonpartisan think tank New America. Yet the Trump administration is far more likely to issue strong calls for national security when Islamist militants are the perpetrators than when it’s a white supremacist.

Harris pointed to the distinction when it was her turn to question Nielsen.

“It is deeply troubling that in your opening comments, when you talk about the threats to our nation, our homeland, to national security, that you failed to mention a report that outlined a very specific threat to us as the American people,” she said.

Booker echoed Harris’s comments, adding that it was personal to him in part because he, Harris, and other senators have received death threats based on their race.

“I receive enough death threats to know the reality. Kamala receives enough death threats to know the reality. Mazie [Hirono] receives enough death threats,” Booker said. “When the commander in chief speaks, or refuses to speak, those words don’t just dissipate like mist in the air; they fester. They become poison; they give license to bigotry and hate in our country.”