because the opinion police punishes good opinions

That's a losing argument. Any example you give I'll just side with the opinion police on. You've got to come up with something better than that. My argument works really well for example because even if all of someone's opinions are correct, acting ashamed of them would still be bad. Shoot, it might even be WORSE to act ashamed of correct opinions. Can you come up with a reason why it would be bad for the opinion police to access someone's data, even if the opinion police have good intentions?

The purpose of private communication is not to hide an opinion. It is to avoid being spied on. The spreading of opinions and tools for public broadcast of information are a different matter.