I don't know if Google is different in this regard, but every tech company I've worked at has forbidden me from "actively defending my employer's values on forums". Maybe not in so many words, but at the very least there's a prohibition against commenting on the company's business on the internet. PR depends a lot on message discipline, which is not what you get from random employees jumping into these arguments.

Ive even created an account to answer this. It's true that most of these companies have cultural values trainings and a bunch of policies, but it's naive to assume that the hired top 1% will follow these policies or even take them seriously. They are smart enough to not get caught (as if anybody cares to catch them), but that's about it.

The today's employment model is a no strings attached contract: the employment can be terminated for no reason at any moment without a notice. This is a double edged sword: not only it gives the company flexibility to fire anyone they don't like, it makes employees mostly indifferent about the company as long as it cuts the paycheck. A typical software engineer does a 4 year gig and when the stock vesting plan ends, he moves on to another gig. There is no reason to take seriously policies of a company he worked at 10 years ago. And regarding evaluating promotions thru the cultural values lens. Yawn. There's no money in promotions.

For a cult to be successfull, its members need to be bound by something more serious than a company values training they watch once a year.