When asked about it, Heinlein and Haldeman have each said how much they enjoyed the other's book.
I don't doubt it.
- I enjoyed both books. And I'm the smartest guy I know.
- Heinlein had gone through his "hippy phase" by then. "Starship Troopers" was written in 1959. "Stranger In A Strange Land", was published in 61, which might as well have been a hundred years later, culturally for the U.S., and "The Forever War" came out in 1974. And in '73 He'd published "Time Enough For Love", where Lazarus Long was screwing his own (semi)identical cloned twin sisters/daughters, and travelling back in time to 1917 to screw his own mom.
So I get the sense Heinlein was a pretty open-minded guy.
And in his books, I never got the sense Heinlein was a blind patriot, or would approve of the implied industrial/military complex cabal that got humanity into "mistaken" war with the Taurans in "The Forever War".