Google CEO Sundar Pichai/Note to Employees:

The memo has clearly impacted our co-workers, some of whom are hurting and feel judged based on their gender. Our co-workers shouldn’t have to worry that each time they open their mouths to speak in a meeting, they have to prove that they are not like the memo states, being “agreeable” rather than “assertive,” showing a “lower stress tolerance,” or being “neurotic.”

Gender differences in personality in personality are well-researched and well-documented, including the traits of Neuroticism, Agreeableness, and Assertiveness. There have been hundreds of studies, spanning decades, consistently confirming gender differences in the distribution of these traits. For instance, per Weisberg, Deyoung, and Hirsh (2011):

Neuroticism describes the tendency to experience negative emotion and related processes in response to perceived threat and punishment; these include anxiety, depression, anger, self-consciousness, and emotional lability. Women have been found to score higher than men on Neuroticism...

Agreeableness comprises traits relating to altruism, such as empathy and kindness. Agreeableness involves the tendency toward cooperation, maintenance of social harmony, and consideration of the concerns of others (as opposed to exploitation or victimization of others). Women consistently score higher than men on Agreeableness and related measures, such as tender-mindedness. 

Women tend to score higher than men on Warmth, Gregariousness, and Positive Emotions, whereas men score higher than women on Assertiveness and Excitement Seeking.

These are differences in the group distribution of Neuroticism, Agreeableness, and Assertiveness. They say nothing about individual women and men. And they aren't even large group differences. Per Weisberg, Deyoung, and Hirsh:

All of the mean differences we found (and all of the differences that have been found in the past...) are small to moderate. This means that the distributions of traits for men and women are largely overlapping.

I'm a woman and find the research on gender differences fascinating - certainly not threatening. Nor does it bother me that biology plays some role in these differences. Why should this information be threatening? Group differences say nothing about individual characteristics. I don't take it personally that women, on average, are more agreeable than men. What I do know is I'm not particularly agreeable.

So some Google employees are upset. That in itself is not sufficient reason to fire the person whose statements upset them. Doing so only reinforces the notion that women are delicate creatures whose feelings must be protected. Better to have encouraged a lively discussion.

Reference:

Weisberg, Y. J., DeYoung, C. G., & Hirsh, J. B. (2011). Gender Differences in Personality across the Ten Aspects of the Big Five. Frontiers in Psychology, 2, 178. http://doi.org/10.3389/fpsyg.2011.00178