You're completely misunderstanding what has been put to you.
If a master key exists for every lock it effectively renders the lock useless. If I obtain that master key I can access every door in the world. A criminals dream.
Your thinking essentially equates to castrating all males because some are paedophiles and rapists. Or to take a more popular example, some Muslims are terrorists so let's ban Islam.
Let's take this further. Some people commit crimes in their own houses, so let's install CCTV in all citizens houses.
You're assuming the whole world is like you, which it clearly isn't otherwise encryption wouldn't exist
It has been taken way out of proportion and way blown out of water.
The whole Apple vs FBI crap is Apple's PR machine turns to maximum. There is articles debunk Apple's claim. And the master key crap is none sense. Apple can always update its software and encryption method.
You can think whatever you want, just because there is possibility that hacker can steal a master key, so you won't do. It is lazy ass thinking and good PR to fool people. It is like there is possibility that terrorist can get a gun, so let's ban all guns.