I suspect they don't care, thus don't know why. This group seems to be so narrow minded that they allow confusion generated in their own minds to influence how the rest of the human population must be.
We don't hurt them or anyone for that matter. We confuse them though. Why indeed try to wipe us out. Have we not proven time and again that gender doesn't affect/impact contribution to society? The narrowly defined acceptance of others just helps them keep their bigotry and hatred. They'll claim that it's "just wrong." Wrong for whom? We are just folks living the best life we can, within the law.
Pursuit of Happiness my eye!