I contend that's a very slippery slope, because where do we draw the line and say: If you break only these laws, it's ok so long as you're "doing it for America" but if you break these other laws, that's going to far. America should not be an excuse for unlawful behavior.
Laws exist, morally right or wrong, so that they can hopefully be applied equally to everyone. That never happens, but we cannot just turn a blind eye to some crimes versus others because of morality, or "doing what is right" for America. Ms. Manning broke a law willingly, knowingly, with full appreciation for her actions. She has admitted doing so in response to American policy towards gay marriage. She's guilty, and she should be punished.