I just saw the new film about Daniel Ellsberg and I'd have to rank him at the top among heroic figures of the Vietnam era. He did, perhaps, more than any other person to end the war. Other heroic figures, IMHO, would include the Catonsville Nine, Noam Chomsky, and Howard Zinn.
Of course, any computer scientist could consider Chomsky a hero "simply" due to his contributions to linguistics. And perhaps I overrate the Catonsville Nine, having never heard of them before I moved to Catonsville. Or maybe I'm just too young.