I know that this is an unpopular opinion on this thread, but Pinchar also made the right move from a legal perspective.
James' memo created a hostile work environment. And legally, that's all it takes to support terminating his employment for cause.
1) He claimed that biological differences were responsible for the behavior of his female co-workers. Yes, he actually says that in the section "non-bias causes of gender gap in tech." If you can't see why that's offensive, try replacing that sentence with "Biological differences are responsible for the behavior of blacks. Or latinos." Legally, this single section, by itself, disseminated on an internal company board, was enough to create a hostile work environment for his female co-workers.
2) Then he goes on to say that "diversity" candidates get special treatment. They get a lowered bar. His words, not mine. So now he's implying that many of the "diversity" candidates only work at Google because they weren't held to the same standards. And unlike his earlier statements about biological differences not applying to any specific individual women, he doesn't qualify this statement--so he's lumping all of his female and non-white co-workers together. This section, on its own, would also be enough to create a hostile work environment for all of his female and non-white co-workers.
3) Then he goes and says the Left denies science on IQ and sex. And that their behavior has created a "psychologically unsafe environment." This, by itself, would also be enough to create a hostile work environment for all of his co-workers that would define themselves as liberals. (Note: there's a reason that most companies don't allow overtly political activities or expression like this in the workolace--it's to prevent political hostilities from dividing the workplace.)
That's 3 things he said that legally would have justified firing him. It doesn't matter whether science supports the broad statements or not. It doesn't matter whether his suggestions at the end or good or not. It doesn't matter whether Google leans left or oppresses conservative expression. What matters is that he created a hostile work environment for large swaths of his co-workers with these 3 statements.