"When people use the word "immigrant" as an insult or as a way to degrade people - I take it personally."
The workers were protesting at the South Carolina Medical College Hospital demanding wage increases and union recognition.
Several plan to quiz Perez on his stewardship of the Justice Department's Civil Rights Division, which he now heads.
The crowd demanded Congress pass legislation providing a path to citizenship and other legal rights for the estimated 11 million undocumented people in the U.S.
An assassin's bullet felled the Rev. Martin Luther King, Jr. on April 4, 1968. King had come to Memphis to support a strike by the city's sanitation workers.