Einstein joined the National Association for the Advancement of Colored People (NAACP) in Princeton, where he campaigned for the civil rights of African Americans. He considered racism America's "worst disease", seeing it as "handed down from one generation to the next". As part of his involvement, he corresponded with civil rights activist W. E. B. Du Bois and was prepared to testify on his behalf during his trial in 1951. When Einstein offered to be a character witness for Du Bois, the judge decided to drop the case.