Starship Troopers asked whether it would make more sense to give control over society to those who felt a responsibility to protect it and were willing to prove it through personal sacrifice. That is an interesting question which I wish other SF authors would pick up and run with.

That Heinlein portrayed military service as acceptable evidence of such responsibility is kind of dumb but doesn't deserve being boiled down to "Heinlein said militarism was good, haw haw".