If the US government can force Apple to decrypt 100 phones per year then it seems likely that an unnamed authoritarian regime could force Apple to decrypt as many as 100,000 phones per year. I think that's what this argument is about. Apple could not care less if they have to decrypt some phones for the FBI. This is about setting a precedent to prevent large nation-states from forcing Apple to spend millions of dollars on engineering time.
The FBI and NSA understand this full well but they are ignoring this issue and making this ugly. Foreign dissidents are irrelevant to the US government.
If Apple has to give its source code and private keys to the US then it will have to give code and keys to every nation state in the world. This will end up in the Supreme Court and maybe the missing vote of conservative Justice Scalia will mean that the court is moderate enough to support Apple in this fight. But most other nations don't have a court strong enough to stop the government. In country after country Apple will be forced to comply with the encryption laws.
In the end we are moving into a world where strong encryption will be illegal in the US (and probably in every other country). No phone, computer, or electronic device will be allowed to have unbreakable encryption. And only criminals will use strong encryption.