I have two guinea pigs. (They are CUTE little FUZZIES and I LOVE them. Just FYI.) Sometimes they hump. This bothers me a bit, partly because they're sisters, and mostly because the one being humped generally doesn't like it. The humpee doesn't panic or anything, it's clearly not a major violation, but she's annoyed. She'll make angry noises and she'll wiggle out from under.
And somehow it offends my sexual mores that they insist on acting like the humper is the "winner" and the humpee is the "loser." I never see a piggy happily offering herself for humping. (I often see them humping each other from the wrong end, but to be fair, both ends of a guinea pig do look pretty similar.) They're both female, yet they see the male role as desirable, as the one that brings dominance and/or pleasure.
I shall have to print them very tiny Gloria Steinem books.