Albert Einstein for being a courageous pacifist (one of only three scientists to sign "An appeal to Europeans" pacifist counter-manifesto in response to the earlier "Appeal to the Civilized World" militarist manifesto (signed by 93) in 1914).
J Robert Oppenheimer for leading the top secret Manhattan project despite it being widely known that he'd been a member of just about every Communist Front organization on the West Coast.