Like it or not, I think speaking openly against defined corporate dogma will get you in trouble in most places. He should probably have realized that and adjusted his course accordingly. Outright being fired is a pretty harsh sanction, and in this case it probably only came to this after the story blew up and Google had to exert damage control in public. A more conventional response would be an uncomfortable talk with your manager and the implicit warning of your career being sidetracked. That alone is enough to keep most people in line.

I don't think the core of this matter is if he was right or wrong, or if he overstepped the red line of PC. I think it's about any culture or any company having things that you shouldn't say. You can challenge these but you do so at your own peril. I think if a Google employee wrote a ten-page, widely circulated, manifesto on the ickiness of ad trackers, he or she would get into similar trouble.