That same argument justifies slavery because it was legal, since slavery makes profits. Your argument is also subject to the ad-hominem logical fallacy [1], and does not actually counter the idea that Google is harming society and that employees should contribute their efforts elsewhere. Additionally, this appears to be the author's attempt to change society, to the greatest extent they can do that is unique to them. They do however, volunteer extensively, in their "Beyond Google" section, weakening a significant part of your ad-hominem argument.

Overall, the author is right in trying to promote people to leave Google, as remaining quiet weakens the whole point of them leaving.

[1] https://en.wikipedia.org/wiki/Ad_hominem