Firing this guy was just a PR move in order to keep things under control. The memo was accurate and I know that Google is going to learn from it even if the guy has been sacrified.
I disagree. His manifesto is pretty clearly core political speech protected by the First Amendment, so Title VII would be unconstitutional as applied if it operates to force Google to suppress such speech. Unfortunately there is no precedent clearly establishing this, so the mere threat of lawsuits (and accompanying legal expenses) may have been a factor in Google deciding to fire him.
I don't see anything good coming out of this.
I speculate (without much evidence) that Google's intention is to manage PR and deflect attention away from their actual lack of diversity. http://time.com/4391031/google-diversity-statistics-2016