This concept Kerr puts forward that criminals will become unstoppable given too powerful crypto is so laughable to anyone who understands cryptography as to be a complete waste of time. For a government built on balance of power and a long history of pushing the limits of that balance, the need for strong crypto is inherently obvious.
You can't issue a warrant for someone's private thoughts, no more than you can issue a warrant for my encrypted diary. It's not actually a 4th amendment issue, it's really an issue for the 5th.
What Apple has done, is take themselves out of the legal loop, where they shouldn't have been in the loop in the first place. Proper crypto is a win-win where I don't have to trust Apple, and Apple doesn't have to trust me. I doubt Apple is actually 100% there, but maybe close enough to stop the government from co-opting them into their investigatory responsibility.
It's perfectly obvious and reasonable that the manufacturer of a diary, e.g. Moleskin, should not be on-the-hook to reveal to authorities everything you write using their product. Similarly, before the Internet and cloud-era, it was perfectly reasonable that the manufacturer of a computer was not on-the-hook to reveal everything produced with that machine.
It's just a quirk of technology that these systems are easier to implement in a 'centralized clear-text' manor, exposing the data to 3rd parties, and therefore government warrants against those 3rd party copies. They never used to be centrally accessible, we've seen the damage a clear-text central store inflicts, and if we've learned anything from it, we won't ever return to this broken model again. Over time crypto will enable many of the 'easier to do centrally' type of services, performed over ciphertext, and without compromising individual privacy.
At this point I think Kerr is just trolling for the page views, since he doesn't seem to have learned anything from the extensive and thoughtful comments his first post elicited.