I think that it's really interesting that conversations about venture capital and conversations about engineering both get to be lumped into a more general conversation about sexism in Silicon Valley. A lot of engineers have a good bit to say against the existence of widespread sexism in engineering, myself included. Engineering in computer science has long been represented by a nearly nonexistent barrier to entry ou…
The idea of there even being a completely objective way to evaluate people is already suspect. I'm pretty sure, for example, that there are many teams where spending long hours in the office will, all else being equal, be considered a good sign. And of course, when decisions about promotions are made, it doesn't hurt to have cultural rapport with your superiors. And that may include football, or being a useful teammate in Counterstrike more often than a shared appreciation of theatre.
It's really hard to objectively evaluate programmers, and there are many disciplines where it was shown that they do discriminate even though they would profess to be completely objective. One famous example is the hiring of musicians for orchestras, where behind-the-curtain auditions resulted in many more women getting hired than before.
Note that I'm pretty sure these people making hiring decisions did actually believe they were being objective. They did not intent to do any harm. But that's not enough. You have to actively work against some parts of human nature, and try to find ways to make it impossible for yourself to fall into such traps.