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".
That said, there are lots of instances of the clerk-typist being told to grab his rifle and fill out a billet for a patrol and similar things --- RH actually speaks to this and other similar, but broader concerns in _Starship Troopers_
"If you have to explain satire to someone, you might as well give up".
It's among his weakest novels but I'm not sure how anyone would derive "genocide" out of it. IIRC, it was a plot point that the invaders also treated Asian-Americans brutally.
To me it's one more sign of how masterful a storyteller Heinlein was that his embrace of the contradictions was conscious and not just a result of some sort of inner conflict.
Stranger In A Strange Land is so creepy, I started to wonder about the sanity of Heinlein. A sex cult around a pseudo-alien? C'mon. It feels like it was written by a 14 year old.
I would submit Incandescence as the best sci-fi novel ever written.
But tastes obviously differ.
In a world with both Greg Egan and Ted Chiang writing sci-fi, one has to exclude their novels from any best-of comparisons just to give other authors a fighting chance.
People contain multitudes.