Relevant, posted farther down: slatestarcodex.com/2017/08/07/contra-grant-on-exaggerated-differences/
If it's a combination of society, preferences, and biology, it could easily be 80/20 (that's the incoming graduate mix). There are many fields that are 25/75 in the other direction and we see little outcry. If discrimination made it 82/18 instead, then yes fix the 2% gap, but it's also possible that positive discrimination is already taking place (http://archive.is/Nt4G8) due to the last 5 years of diversity discussions and programs at Google, and the unbiased ratio is 82/18.
If he's already seeing conscious bias in favor of female candidates, that deserves a debate on whether it's worth it to increase representation, whether diversity is worth some tradeoff, in the same way that college admissions affirmative action leads to the same flamewar.
Incidentally, California voters made any sort of affirmative action, even favoring an under-represented group, unconstitutional for schools. So what's happening at Google in the form of diversity fast-track hiring would be illegal at UC Berkeley, interestingly enough.