The most important bit is that Apple can (and in fact, was asked to) make the change only work on a single phone. As in, there is no fear of it "falling into the wrong hands" as the FUD goes. If you believe in the security of cryptography, then you believe they can make this change cryptographically device locked.
Then once that happens: they have both precedent and legal case law on their side to compel Apple, or Microsoft, or Cisco, or Google, etc. to do the same for another secure product.
> Then once that happens: they have both precedent and legal case law
"Precedent" and "case law" are the same thing (and "legal case law" is just a silly construction), so it doesn't really add anything to say you have both of those, instead of one or the other.
All this case law talk is irrelevant. If Apple actually just voluntarily did this one time it wouldn't really set a legal precedent. Fighting it will probably set a legal precedent. And they are doing it on a case that maximizes the FBI's argument that this is needed for national security.
But sure, Apple will end up having to do this for a lot of phones the FBI has. But why is that a problem?