Hmmmm... In Stranger... the wonder at that was a reflection of a character's conditioning, YM, not necessarily RAH's.
In several of his books there are "gay" intimacies either directly stated or implied - for example, in which story I don't recall, Woodrow Wilson Smith (Lazarus Long) discusses trying a couple of homosexual encounters when he and one of his close buddies were young men, but it wasn't all that exciting for either one of 'em so they just washed their hands and went out to play ball afterwards. His usual view of homosexuality was fairly neutral, especially for a straight man from his era.
On the other hand, some of his characters are definately anti-gay and anti-eunuch in their worldview. One that stands out in this is Jubal Harshaw from Stranger (who is also the character I believe initially wondered about Mike's orientation, not Jill, Jill straightened Jubal (and Ben Caxton) out on that ...

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Oh! one more item: "I Robot" was by Issac Asimov, not Robert Heinlein, Dave. I met Issac once back in Eatontown, NJ, and was lucky enough to actually have one of his books in my car at the time and got him to sign it. A fascinating guy in person, and an incredibly agile and quick mind - even if he WAS afraid of flying ...