At a rally in Huntsville, Alabama, on Friday, Trump mused: "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a bitch off the field right now, out. He's fired.' "
Jackson Lee, who represents central Houston, demanded to know which NFL player's mother Trump was insulting.
"That is racism," Jackson Lee said during a special order of the Congressional Black Caucus. "You cannot deny it."
Then Jackson Lee took a knee.
"I kneel in honor of them," she said. " . . . I kneel because the flag is a symbol of freedom. I kneel because I am going to stand against racism."
Virtually all NFL players who appeared on the sidelines Sunday locked arms, some standing, some kneeling, in response to Trump's campaign to "fire or suspend" players who kneel during the national anthem and, on Sunday morning, his call to boycott the NFL entirely. The president's stance — which he adamantly defended Monday on Twitter — has been widely rebuked by the league, owners and players.
He also pushed back against the idea that his opposition to the NFL and its kneeling players was about race.
On Monday, Jackson Lee and the Congressional Black Caucus joined the chorus of criticism. Jackson Lee previously called on Trump to resign following his sexist attack on MSNBC's "Morning Joe" co-host Mika Brzezinski, who he said was "bleeding badly from a facelift."
"There is no basis in the First Amendment that says you cannot kneel on the national anthem or in front of the flag," she said. "There is no regulation that says these young men cannot stand against the dishonoring of their mothers."
Civil rights leader Rep. John Lewis, D-Ga., a fellow member of the Congressional Black Caucus, also spoke out against Trump's comments on Monday, saying that "young people kneeling today are following a long tradition," referencing civil rights leaders' tradition of kneeling in protest.
"During another period, we knelt," Lewis wrote in second tweet. "There is nothing wrong with kneeling down to stand up against injustice. It's protected by the Constitution."
Earlier Monday, Rep. Cedric Richmond, D-La., chairman of the Congressional Black Caucus, condemned Trump's attack on the NFL and Colin Kaepernick, the former San Francisco 49ers quarterback who began kneeling during the 2016 preseason to protest police treatment of African Americans.
Richmond also called for a stronger rebuke of the president. He said he had read more than a dozen statements from owners and coaches about Trump's "petty and prejudiced attack," but none of them addressed the root cause of Kaepernick and others' protest.
"They are taking a knee to protest police officers who kill unarmed African-Americans — men and women, adults and children, parents and grandparents — with impunity," Richmond said. "They are taking a knee to protest a justice system that says that being black is enough reason for a police officer to fear for his or her life."
In the NFL, he said, 70 percent of players are black, which means they and their families and friends have "experienced racial profiling by police that leaves too many unarmed African Americans injured or dead."