It's not that a company like Google is going to release a Google Gulag product after years of working on it in secret.
What people are worried about is that the various pieces of technology that Google is developing can be used to make a horrible dystopian future and that one day, even if Google as a corporation, or the individuals who make up Google as employees decide to fight against it, they will be unable to stop a fascist government from using that technology to do exactly as is described by OP, or even worse.
There are unintended consequences to everything, and you may think that America is the freest nation on Earth, and that Google is the greatest company ever, but that could quickly change.
It could happen here, and we must be eternally vigilant.