There's a lot of things you have do in the military for the sake of discipline which you might not do in civvie street. Folding your underwear and saluting jerks are only two which come to mind.

Very few bureaucratic organizations, government, business or otherwise would tolerate public utterances by its members which slammed organization policy. Neither does the military restrict free speech in private or public venues, except when that speech becomes picked up by the media and publicized by those opposed to government policy. After all, government policy is, by definition, military policy.

An institution which routinely asks its members to engage in almost-suicidal behavior and punishes them if they refuse could hardly function if policy decided way up the chain of command was routinely questioned by some grunt on the line. Part of the way servicemen are indoctinated to behave in this fashion is to make them instinctively obey even in inconsequential and insignificant acts. If you can't get a man to shine his shoes three times a week he's not likely to pick up a defective hot round and throw it over the side on command.

OTOH, active duty military types are not discouraged or punished for respectfully pointing out to superiors that they feel an order is unwise, in fact, it's their job. But once they have voiced their recommendations, they are still obligated to carry out the order if repeated, regardless of how idiotic it may turn out to be later.