Sen. Cory BookerCory Anthony Booker2020 Democrats challenge Trump's use of troops at Mexico border Election Countdown: Florida fight ends with Scott, DeSantis wins | Dems see Sunbelt in play for 2020 | Trump to campaign in Mississippi ahead of runoff | GOP wipeout in Orange County | Ortiz Jones concedes in Texas House race Booker to make second visit to New Hampshire in weeks MORE (D-N.J.) criticized Homeland Security Secretary Kirstjen NielsenKirstjen Michele NielsenDHS chief says Trump administration to appeal asylum ruling 'as quickly as possible' CNN's Toobin on asylum vs. economic immigration: You can't come to the US ‘just because you want a better life’ The Hill's Morning Report — Are Pelosi’s Democratic detractors going too far? MORE as complicit with President TrumpDonald John TrumpTrump: WHCA picking non-comedian for headliner a 'good first step' Five takeaways from Mississippi's Senate debate Watergate’s John Dean: Nixon would tell Trump 'he's going too far' MORE for saying she did not hear him say the United States should not accept immigrants from "shithole countries."

"When ignorance and bigotry is allied with power, it's a dangerous force in our country. Your silence and your amnesia is complicity," Booker told Nielsen during a Senate Judiciary Committee hearing. 

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Nielsen said during questioning at the hearing that it was "possible" Trump used the vulgar term to describe Haiti and other countries during an Oval Office meeting attended by several lawmakers, but she could not hear him using the expletive. 

"It was a meeting of 12 people. There was cross-talk," Nielsen told the panel. "Anything is possible. I can't testify to what I don't know." 

Booker, an African-American senator, called Trump's reported remarks "the most vile and vulgar language."