I don't think there's a moral duty to do so, but neither do I see how doing so hurts/is wrong. You're only opening tech space to people that might be as or more talented that people already in the pool, but that might be lost because they were never told "you can actually do this".
There is an implied assumption that there is a moral duty to help get more women in to CS. I have yet to hear a reason for this that does not reduce to "Just because". (e.g. the notion that in ideal, fair world, programming jobs would be split 50/50, which is basically an article of faith, opinion.)