I've also read that there was a common attitude in place, at least in Athens, that heterosexuality and marriage was for procreation and that 'true love' could only be between 'equals' --ie, same sex.
Modern retellings of the myths typically bowdlerize out the homosexual aspects, but they're most certainly there. The ancient greek attitudes about homosexuality were far, far different than our own.
As to the Vikings, that's a different story. I'm not aware of any particular penchant for homosexuality among the ancient Norse, but I do know that much like the Celts they highly respected their women. Thor was married in the myths, and his wife was the one person god or mortal he wouldn't cross.
Too often, these stories and the cultures they represent get filtered through a modern cultural lens rather than portray the actual mores of the time.