Because his argument is that even adjusting for the pipeline issue, women and minorities are under-represented. In other words, even if you fixed the pipeline issue, they would still be discriminated against and under-represented because of bias.

His numbers are all over the place. Most of the stats he provides are for executives and investors which don't require STEM degrees, yet he uses STEM graduation as his initial stat.

I don't even know what this means:

"0% of partners at some of our largest Bay Area VC firms are women"

So > 0% of partners of the largest Bay Area VC firms are women, since he qualifies the statement with "some"?

I think it means that there are large firms whose partners are 100% male.

The argument is that the availability of choices is not the same between the sexes. Part of the problem is that so few women are in the engineering disciplines that when young girls make the decision (and this is of course, a simplification...it's not the decision, but hundreds of little decisions that factor into a career choice), they aren't as inclined to go into engineering because they just don't see themselves as being engineers. Nor do their parents, peers, social groups, etc. So it's an unfortunate feedback loop.

To use an anecdotal example...I wanted to be a journalist growing up, but that was not something my parents heavily encouraged, when all of the other Asian immigrant kids went into med school or engineering. I ended up just doing journalism and engineering in college but I credit that to my parents being relatively easy-going about what path I choose. I'd like to say that I graduated with an engineering degree because I'm especially talented for it, but more likely, it's just that I didn't face much resistance and I also saw a lot of other people "like me". I doubt this is the same for women.

The women not choosing to become engineers are choosing to do something though. In fact there are more women than men graduating from college today. Women are succeeding in higher education, just in fields of their own choosing.

I don't think anyone should look at the choices people make for career and say it's problematic because they didn't help a gender stat go up in a field they weren't interested in.