The battle over climate change in the U.S. Senate spilled into another contentious arena of U.S. politics on Thursday: race relations.

At a hearing to discuss the economic impact of legislation to combat global warming, the head of an African-American business organization accused Environment and Public Works Committee Chairwoman Barbara Boxer of being “racial” and “condescending.”

During a tense exchange, Harry Alford of the National Black Chamber of Commerce said he objected to Boxer bringing up other African-American groups as a contrast to the arguments he was making at the hearing.

Boxer had cited a resolution in support of legislation to combat global warming from the NAACP, an African-American civil rights organization.

“What does that mean?” asked Alford, who was a witness at the hearing. Boxer responded by pointing out a positive comment about the resolution from the leader of another African-American group, 100 Black Men of America.