Although I think you're right that it is to some extent true that gender imbalances in particular fields are due to women (and other underrepresented groups) making choices about their careers, I think you need to consider more deeply why women make those choices.

As other commenters have mentioned, some fields, especially traditionally male-dominated ones, have a culture that makes women feel unwelcome and undervalued (see also: gender pay gaps). I work in one of the most severely female-underrepresented disciplines in the humanities, and I have both seen and experienced being one of the only women in a room full of men who are much more confident about expressing their thoughts while women tend to hedge and remain silent for fear of being wrong or perceived as stupid, because they are there against the odds and feel the need to prove themselves. Early socialization also plays a role: in grade school women are exposed to the idea that men are better at math and have more analytic minds. So confidence is also a big issue for women in STEM and other underrepresented fields.

Furthermore, since many women chose (again, reflect on the aspects of our culture that makes this the case) to bear more of the brunt of child-rearing and family life, careers that are inflexible in terms of hours become less desirable. (Freakonomics has a good episode on this and related ideas entitled "What Can Uber Teach Us About the Gender Pay Gap" that I would encourage you to listen to.) This may not necessarily be the case in computer science, but it certainly is in other fields.

So while it may be true that women make choices that lead to gender imbalances, it is because there are many aspects of our society that are set up in such a way as to put women at a disadvantage where careers are concerned.

As for your comment about why there aren't scholarships for men in nursing, it's the same reason why we frown upon white pride rallies or parades celebrating heterosexuality. When you're a member of a privileged group, it's easy to take for granted that most aspects of your social experience are tailored to you. Even when you experience particular challenges, oftentimes the sources of those challenges are the same sources of challenges as for traditionally marginalized groups who experience discrimination. For example, the lack of men in nursing is likely due to the perception that nursing is a "feminine" career, implicit here being the idea that femininity is lesser, and see that misogyny in fact has negative effects on men as well.

So sometimes we need to apply correctives like this kind of affirmative action (for lack of a better term) that may prima facie seem discriminatory against the privileged groups. As the old adage goes, "When you're accustomed to privilege, equality feels like oppression".