"I remember in a later book in the series (Xenocide?), there were many off-planet colonies, and on those homosexuality was the norm and heterosexuals were seen

"I remember in a later book in the series (Xenocide?), there were many off-planet colonies, and on those homosexuality was the norm and heterosexuals were seen as "weird"." I don't have a copy of Xenocide at the moment to check but are sure you're not thinking of 'The Forever War' by Joe Haldeman?