As I already explained diversity of thought isn't appropriate in a workplace. If it were, that would mean bullying and teasing would be appropriate. The problem is where to draw that line.
Where Google drew this line was firing someone for implying some people were undeserving of their jobs due to the biological argument. This declaration breeds hostility and is an outright attack on the qualifications of his coworkers.
As far as I know, affirmative action is practiced in colleges while companies practice seeking diversity out of the same pool of qualified applicants. I agree with this and think it's great companies can make their own decisions.
I've applied to jobs for startups where I would have been the only woman on the small team and bro culture was strong. I don't fault them but I declined those positions. I've gravitated toward companies like Google and their diversity policies have attracted talent like me. Companies do this in their own self interest.
I just want to clarify I'm not at all offended that the memo writer wrote what he did. I would feel offended if someone I worked with felt like there were too many woman in their office while there were only 5% and I felt that they were all qualified.
Even measuring qualification is tricky as unless you are someone's manager. More often than not, I've witnessed men make poor assumptions unaware of their own prejudices. For example, I got accepted to a very good college. I was surprised as to how many men thought it was only because I was a woman. However I knew for a fact I got better grades than them. I simply didn't advertise mine.