You got the point of that movie all wrong. Mutually assured destruction is a game where the only winning moving is not to play, because it is mutual, meaning either choice is equally doomed to the same outcome. "Two undesirable outcomes" is not a good enough excuse to simply not participate. By definition, one of those outcomes must be preferable to the other, and that's what you should vote for, while you continue to work outside the ballot box to push better candidates and better policies.
"All that is required for evil to triumph is for good men to do nothing."