The question wasn't what should they do, it's why are they doing what they are currently doing? That said, obviously the point of remaining is so that they can

The question wasn't what should they do, it's why are they doing what they are currently doing? That said, obviously the point of remaining is so that they can refuse those worse orders when they come, so that they can convince their peers to do the same or temper their actions, so that the administration needs to worry about pushing too far lest that wave of resignations comes at a critical moment. Alarming though the pattern may be, this is neither a clear cut violation of the constitution nor likely to be a major turning point in the administration's public support. Leaving now would be ineffectual - there is no plan in place to take advantage of a few resignations to put a serious damper on the current plans, nor will it stop what's to come. The people who resign now may feel good about themselves, maybe enough to justify the potential hardship they and their loved ones will suffer as a consequence, but they deny the rest of us a key resource. Resigning is a weapon that can only be fired once; it would be selfish and stupid to waste the shot.