Mmm. You make a strong point. It could at least be overlooked in a stronger context.
Taking it from a slightly different angle, though...
I think that this particular biological quirk, executed as it's described here, can only be made to work (in the Super-hero format, anyway) if it's a sidelong point, that you've got a whole different story to drag you along before you can think too hard on the implications.
Taking it away from this story, even if it were dropped into something along the lines of The Left Hand of Darkness (goddess, I hope I'm thinking of the right one...I read LHoD and the Dispossessed pretty much back to back and I've jumbled them somewhat in my brain) - making it the focal point of any story that's not clearly primarily allegorical simply invites the reader to think long and hard on it, and in this case, the elements that wouldn't work in reality also don't work well in the story.
Similar set-ups can be made to work, obviously, but there's too many screwy elements in this one - the whole species shifting to the same sex, en masse, and developing a pathological hatred for the other sex being the primaries - to work, unless all the 'this is a completely non-literal morality play' flags are tripped.