At a breakfast celebrating Martin Luther King Jr., top Massachusetts politicians Monday pilloried President Trump, calling him a racist and a bully. They said his words and actions tarnish the magnanimous values that have animated generations of Americans. And they pledged battle against the New York billionaire.

The anti-Trump jeremiads came amid a roiling national debate over the president’s feelings about people of color. And they were delivered days after he reportedly questioned why the United States is accepting immigrants from “shithole countries,’’ including Haiti, El Salvador, and African nations, rather than from places like Norway.

“We face the challenge of an openly racist president of the United States,’’ said Senator Elizabeth Warren to applause at the convention center in South Boston. “Donald Trump is a racist bully and we know how to deal with bullies. We do not back down. We do not shut up. We fight back.’’