First of all, police and firemen in the U.S. get a similar level of respect to the military. We just celebrated Veteran's day, so the emphasis was on the military, but at other times the police and firemen get the focus (to see an example of this, spend next September 11th in New York City).
That being said, the military experiences sacrifices (which I and others have mentioned) that police and firefighters don't: frequent moves, long time away from home, loss of rights, etc. Also, while I won't comment on the quantitative difference in danger levels between law enforcement and the military because I don't have statistics handy, I will say that there is an enormous qualitative difference in knowing that you are in proximity to an armed organization that exists for the express purpose of killing you and your fellow citizens.
>The assumption that everyone in the US army joined up to serve the Constitution etc and is universally motivated by "sacrifice" is very suspect.
Every single person who joins the U.S. military swears an oath to support and defend the Constitution, so even those who join for other reasons know what is expected of them.
You talk a lot about motivations for military service, but it's clear that you don't understand the U.S. military. The reality is that almost nobody joins for any single reason. For example, the OP gave a very complex and not entirely clear explanation for why he had joined, which included a certain amount of patriotism. There are certainly some folks who join just to get something they want or need, but the overwhelming majority are motivated at least in part by a genuine desire to serve their nation and the ideals it embodies. Also, I never said that anyone was motivated by sacrifice: I said that they accept sacrifice because they are motivated by other factors. (That being said, there probably are some individuals who really do seek sacrifice as an end unto itself.)
However, even those individuals who joined the military for purely selfish reasons deserve respect and gratitude: they did make sacrifices, and those sacrifices did support our nation.
In regards to your example of Japanese soldiers at Nanking: the moral worth of a cause is not completely subjective. If a person believes that spreading totalitarian rule is noble, that person is morally wrong. On the other hand, preserving a system of self-government is morally good. You can certainly argue that a particular war didn't actually do anything to preserve said system, but our service members don't sign up for particular wars, they sign up to serve our nation.
You contradict yourself here:
>The rest, the vows and the sacred oils and the lady’s favors, they’re silk ribbons tied round the sword.
>What distinguishes him from a mafia hitman is that...he is part of an organization subject to socially approved rules and regulations...
Those "vows" that your fictional character dismisses as "silk ribbons tied round the sword" are the same as the "approved rules and regulations." Furthermore, they are not merely "socially" approved. The rules of war as they exist today have been refined over the course of generations for the purpose of making sure that wars are fought between legitimate combatants, with everyone else left out of the violence to the greatest degree possible.
>And a description like, "individuals volunteered to make tremendous sacrifices in service to a noble ideal" would fit a policeman perfectly, if you happen to assume that every policeman chose his job only because he wanted to dedicate his life to justice and protecting his fellow citizens.
Actually, you don't have to make any such assumption because his motivations don't really matter: whatever his reasons for taking the job, he is making sacrifices, and his work directly contributes to justice and the safety of his fellow citizens. It doesn't matter why he chose to take the job, it only matters that he knowingly accepted the sacrifices that come with it and that he diligently pursues his duties.
>And yet we don't expect random people to thank every policemen "for his service".
First, nobody "expects" anyone to thank veterans. Second, I have seen plenty of people thank policemen, firemen, and teachers for what they do.