While serving as President of the American Jewish Congress, he represented the Jewish community as an organizer of the August 28, 1963, March on Washington. He came to the podium immediately following a stirring spiritual sung by the gospel singer Mahalia Jackson and just before Martin Luther King Jr. delivered his famous "I Have a Dream" speech. Dr. Prinz's address is remembered for its contention that, based on his experience as a rabbi in Nazi Germany after the rise of Hitler, in the face of discrimination, "the most urgent, the most disgraceful, the most shameful and the most tragic problem is silence."