Using violence to counter violence is still violence. Using sexism to counter sexism is still sexism. Simply put, An eye for an eye will always leave two blind people no matter how justified one feels it is.
I do not consider it discriminatory to make an extra effort to recruit an under-represented group. Hence, I don't see this as "sexism to fight sexism."
Which is fair enough. I'm not going to get into that. I just wanted to point out the fundamental assumption in the notion of "fighting sexism with sexism."