The government doesn't want a backdoor. They want Apple to remove barriers slowing and limiting the number of guesses at the key. If the key were longer, those barriers wouldn't be needed. So this isn't about strong encryption, without backdoors. It's about some sort of right to short, memorizable keys, and technical barriers protecting them.
Now maybe we have such rights. (I don't think so, I do think we have a right to strong encryption and strong keys.) But that's a very different argument than "backdoors are bad". If Apple's case is "no backdoors", they make that argument look not like a technical argument but a preference to not comply with a warrant. Non-technical people could easily get the idea that technical people say "no backdoors" when they just don't agree with the government's ability to execute warrants, and that all the technical arguments about real security are mumbo jumbo to avoid obeying laws they don't care for.
Using strong encryption with phones is a usability issue. If the phone were somehow protected by a strong key, Apple could easily comply with this order and the government still could't read the phone. But they haven't figured out how a user can deploy a strong key in some usable fashion. Well, that's obviously a challenge to phone data privacy. I expect it is solvable. And it is much less an issue in contexts like desktops and laptops.
But we have a right to encryption. We don't have a right to usability. Claiming the two are the same weakens the case to the right we do have.