Chiming in here late.
Everything that I have read about Joe Haldeman (mostly from fellow authours) would support Arthur's speculation that "It's genuine sociosexual speculation on his part, in a Heinlein sort of way." - with my personal opinion that it's in a much superior to Heinlein's way. His speculation (not prediction) and views seemed to me to have been shaped, of course, by Vietnam. Reading him cold, years ago, I reacted that he was profoundly anti-war.
Having read every RAH, starting at about the age of 9, he was (obviously) significantly creative, but not speculative. In other words he introduced characters and ideas to further the story, not to be predictive or due to genuine interest in ideas per se. This became clearer as his so called SF veered into fantasy in later years. His politics did intrude, but in terms of plot and character scenerios were invented and he made them more interesting by letting them act out his preferred ideology. A fine line, but It's what I increasingly thought over the years. A storyteller much more than extropolator. He started writing "capable man" stories for Campbell, continued through his juveniles, and went totally overboard in his last several books. He wrote strong capable women, but with the possible exception of Hazel Stone, they were either cutsie stereotyped or "capable men" with no real difference in character than his male characters (see Friday)
Haldeman is obviously a storyteller, but specifically in the Forever books he was talking about society not just writing creatively. And (I looked it up) he is four years older than me. In no way was his characterization of gay folks anything but positive, particularly for 1974. The point made above that some of the role/assumptions about female sexuality are dated seems right, but with perfect hindsight that can be said about many/most great authors, including Ursula le Guin, the prime early sexual stereotype breaker. Other than the scene described and the fact that his lead characters are, to the best of my memory, all male I think that he does as well as almost any of his (my) period.
Thanks for letting me interrupt from my soapbox.
edit: I deliberately waited to re-read Matt's review until after I wrote the above. He describes with better specifics much of what I thought. Thanks for posting Matt.