I think your viewpoint is at the crux of the debate. We run into a few ethics questions with no obviously correct answers:
(1) If discrimination based on sex is wrong per se, then isn't it unethical for the government to engage in it? (I.e., is it okay to crack a few eggs to make an omelette? Is it okay to sacrifice one innocent virgin to spare the whole village from the volcano?)
(2) Is there an aspect of vengeance to this? And if so, isn't it collective punishment against today's young males, because of some perceived benefit their fathers had (but they don't)?
(3) If the goal is to restore some kind of equilibrium, then how would we know when to stop? And what do you say to those young males who are discriminated against during a period of over-shoot? "I'm sorry Johnny that we wouldn't spend as much time teaching you math as we would your sister, but think of all the girls who benefited!"
(4) How do we choose which supposed social good to prioritize? For example, why is it preferable to increase women's incomes, at the expense of men's opportunities?
(5) Is it truly just for the government to address one perceived inequality (by preferential treatment of girls in school), without putting equal effort into addressing areas where men have traditionally been at a disadvantage (child custody, incarceration rates, etc.)? If the government's policy is only to address those inequalities where women come out behind, then the end-game is apparently not equality, but something else. (Matriarchy? Vengeance? Collective punishment?)