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Sen. Cory Booker (D-N.J.) blasted Homeland Security Secretary Kirstjen Nielsen on Tuesday for repeatedly telling a panel of senators that she did not hear President Donald Trump call African nations “shitholes” even though she was in the room at the time.

In a long and emotional speech, Booker explained why he finds the president’s comments offensive and dangerous. He described them as at odds with the idea that people are judged “by the content of their character” rather than the color of their skin or their country of origin. Booker linked Trump’s words to the rise of white nationalist violence in the United States, noting that anti-immigrant animus has driven domestic attacks on people of color.

“When ignorance and bigotry is allied with power, it is a dangerous force in our country,” Booker told Nielsen during a Department of Homeland Security oversight hearing before the Senate Judiciary Committee. “Your silence and your amnesia is complicity.”

He added, “I receive enough death threats to know the reality.”

Sen. @corybooker: “When the Commander-in-chief speaks or refuses to speak, those words just don’t dissipate like mist in the air. They fester. They become poison. The give license to bigotry and hate in our country.” pic.twitter.com/rbUbhCHRAQ — CSPAN (@cspan) January 16, 2018

Booker reminded Nielsen that she was under oath when she repeatedly said she did not recall the “shithole” comment.

Nielsen responded to Booker by saying that she “abhor[s] violence in all of its forms” and that her department is not ignoring violence by white supremacists. A new report from DHS and the Justice Department on terrorism convictions entirely omitted domestic terrorism.

Sen. Kamala Harris (D-Calif.) spoke after Booker and said she agreed with his remarks. Booker and Harris are the only African American members of the Judiciary Committee. Both are new to the committee, having joined last week.