>I bear some responsibility by choosing this field
You bear 100% of the responsibility for accepting a DoD grant. You can't absolve yourself of some nebulous amount of responsibility because of who's writing the check.
I don't think that's entirely fair. Graduate students are hardly in a position to refuse a funding source. That's up to the primary investigator and even those only have the luxury if they are able to secure other sources of funding. Unless you're saying you would quit your graduate studies or start over and find another supervisor after your lab becomes DoD funded.