The system is designed in such a way that such a scenario doesn't happen, because once you indicate an unwillingness to open that door - you aren't expected to ever open that door (and you're unlikely to be offered the opportunity). You will just continue to operate at the level of your last door opening. This isn't unique to SF, you see this sort of continuous evaluation occur in the corporate world as well.
That is how you end up with a spectrum of SF groups, where some are tasked with difficult but clearly whitehat missions (the bulk of well known SF), illegal but debatably moral grayhat (some known SF but mostly units operating under cover designations), and finally the blackhats that rise to Hollywood level evil (basically Apocalypse Now with no paperwork). So for a late career SEAL the probabilities are pretty good for someone to land between lawful-good and neutral-good. Those are infinitely better odds than what you'd get with some random businessman.
I'd probably share your concern if the military was full of utilitarian statists, but strangely enough it is the direct opposite... well, except for flag officers - they can get a little kooky.