This. I think encouraging women is discouraging in itself. It includes an assumption of power and superiority, and opens them up to doubts and criticism about their technical merits. The best would be not discouraging anybody at all, then those naturally inclined towards the field will be attracted by themselves.

A thing that all of us can do is to get rid of their prejudices for real. We like calling things mysogny and racism and attack, but what they profoundly are is hereditary prejudice which only heals through self-education.

Edit: prejudices are not limited to white males, but we all have them (obviously me too, thus having to do this edit).