Why? He's under no obligation to Google. It's not like they hired him and he has to sign an NDA or be polite. He had a frustrating interview process and vented about it online, it's a pretty human thing to do. Why would that make him a bad employee?
If you were a corporation trying to keep PR positive, would you hire someone that has shown themselves as an outspoken public mouthpiece and tip-toe around them to keep them happy, or just avoid the problem?