The categorical error you make, like the author of the anti-diversity memo, is conflating gender identity with a specific set of "boy" versus "girl" activities. Just because children have strong gender identity does not mean that you can categorize any given activity as "girl-like" versus "boy-like." I.e. there is nothing to show that liking pink unicorns causes someone to have a preference against computer science.
As to our own daughter, I don't want her to be an engineer or a scientist. I want her to be a lawyer, like her mom and myself. I also hated school and don't place much emphasis on education. She's the one who wants to do puzzles and math worksheets and build legos.
Of course, that's anecdotal and doesn't prove anything. The real evidence, to me, is that this association between math/science and men differs dramatically between countries. In Bangladesh, more than 80% of teachers are men (overrepresented compared to the total labor force). And in India, half of science undergraduates are women: http://www.catalyst.org/knowledge/women-sciences. It's really a different societal mindset about what professions are appropriate for women versus men. For example, I grew up hearing my Bangladeshi mother complain about how the teachers in U.S. schools are women, when men make better teachers.
Diversity programs from big businesses have always seemed sick to me. Why does Google want more diversity? Ultimately, because they want to double the supply of engineers and reduce their hiring costs. The idea that I should subvert my daughter's innate interests, and encourage her to follow pursuits that are foreign to her, just so that Google can save money on employee salaries is perverse.
In my view, true diversity is valuing what makes people different. School teachers tend to be female and software developers tend to be male. "Diversity" shouldn't be taken to mean that 50% of developers should be female and 50% of school teachers male. That's not diverse, it's uniform. Instead, diversity should be recognizing that a school teacher isn't inferior to a software developer.