I'm by no means an expert, so I'll definitely bear with you. But your hypothesis more or less matches mine. I do think you underestimate the amount of sexism men experience in nursing and child-education.
Now my problem is that gender ratio is the key metric we seem to be using to measure sexism in STEM fields, and I don't think any policy is going to fix that. We can try and mitigate cultural expectations, but if those cultural expectations are grounded on intrinsic interests, we're going to have a very hard time getting rid of them.
I think you really need to examine your idea that "men bear most of the responsibility". Men always bear most of the responsibility, and that's one of the oldest stereotypes. Men are generally considered to be more responsible for their own actions then women are. I think it's why they get longer prison sentences for the same crime. If you're not an object, you're a subject.
So why do you think men bear most of the responsibility, aside from historical precedent? Are men best situated to fix these problems?
I will note that a lot of new programmers are indian or asian men, which implies to me that tech is pretty good as far as racial discrimination goes. It certainly seems like a welcoming environment for those visable minorities. Or at least more welcoming then most of the alternatives.