The Italian-American Civil Rights League was run by Joseph Columbo, the Mafia Don of one of the Five Families in New York. Columbo was assassinated by Mafia enemies at a big rally of the League. Richard S. Castellano, who played Clemenza, was the nephew of Big Paul Castellano, another Mafia Don who was publicly assassinated.
Paul Castellano was assassinated at Spark’s Steakhouse by John Gotti and his amigos.