There is no way to have a completely secure operating system, safe from hackers and spy organizations and thieves, that is also accessible at the whim of law enforcement. Period.
If we can't trust hosted services to protect our data, and we can't trust our own computers to preserve our data, the right to privacy simply doesn't exist.
The goal of law enforcement isn't to give you secure operating system. It's to find people who they perceive as criminals.
You don't need to persuade me about it. You need to persuade your cops and governments that having your OS secure outweighs their wish to make crime fighting easy.