Conversation so far:
What were Jerry Lewis' political views?
Jerry Lewis was also a world-renowned humanitarian, philanthropist and number one volunteer who supported fundraising for research into muscular dystrophy.
What did Jerry Lewis do politically?
In 1951, Lewis and Martin made their first appeal for the Muscular Dystrophy Association.
What else did Jerry Lewis do, besides making appeals for the Muscular Dystrophy Association?
In 1954, Lewis fought Rocky Marciano in a boxing bout for MDA's fund drive.
How else was Jerry Lewis involved in politics besides make his first appeal for the Muscular Dystrophy Association?
In a 1971 Movie Mirror magazine article, Jerry Lewis came out against the Vietnam War.

Question: What prompted him to take this stand?
Self-contained rewrite: What prompted Jerry Lewis to take a stand against the Vietnam War?