Conversation so far:
what did Leonard Bernstein have to do with social activism?
Leonard Bernstein aspirations for social change were made apparent in his producing a recently banned opera, The Cradle Will Rock, about the disparity between the working and upper class.
what was Leonard Bernstein blacklisted for?
Leonard Bernstein was involved in various left-wing causes and organizations since the 1940s

Question: are there examples of any?
Self-contained rewrite: are there examples of left-wing causes or organizations that Bernstein was a part of?