The same thing can be said of blacks. Like it or not the amount of black CS engineers in Silicon Valley is very, very small. You can't artificially create diversity when none exists in the talent pool.
That doesn't mean it isn't valuable to a company. In any good engineering company, all the best product ideas come from the engineers. That means the more your engineering workforce looks like your potential userbase, the better they are going to be able to serve their potential customers with their new products.
Probably the majority of the users of the hotter social media tools are female. Now I will freely admit at age 47 with a wife and two girls, I don't understand women at all. Perhaps some men are better at that than me, but I think its ridiculous to argue that your 85% male workforce is well in touch with the needs and desires of their 60ish% female userbase. This can't be anything but a problem.
Similarly, black people turn out to be huge users of Twitter. Clearly it provides something for them that other platforms don't. What is that? Well, I grew up in the majority black part of my hometown, so I probably understand them better than your average white guy, and I can tell you I don't understand them well enough to be an authority. You really need to ask your black employees. Note the plural. Several. One token person isn't enough to provide a good perspective.
So yes, there is value to a company in having female and black (and Hispanic, and Muslim, and ...) employees, over and above their basic tech chops. If white guys don't like to hear that, perhaps they should sit and wonder about the fairness of men not getting jobs waiting tables in deference to women, or ugly people not getting jobs as receptionists and actors. Sometimes your background or looks are actually an important part of your job. That's life.