In the country against country conflicts it is good to have companies like Apple on our side. People have noted their cooperation with China but that was relatively modest, e.g., http://www.telegraph.co.uk/technology/apple/11364672/Apple-bows-to-Chinese-demand-for-iPhone-security-audit.html There will always be more demands for assurances that there are no remote back doors but there's no way to prevent that when a phone is in use. China will have to accept the risk if they want their citizens to have the best technology.
Some people also bring up the red herring of encrypted comms. Your statement is along those lines. Encrypted end-to-end text is now used by about a billion people worldwide and no country can intercept those. Secure voice is used by 100's of millions with the same result. But there are workarounds even when the channel is encrypted end-to-end, because the end points are never provably secure.
This is a data-at-rest encryption issue. It is also a case of the barn door wide open and the horses long gone. But there are a few fat cows left and phones are one. Here's a horse that left the barn a while ago::
If the dead terrorist had one of these the FBI would have absolutely no recourse. The security used in the product pictured is exactly the same as Apple: constrained passcode input, passcode hash delay, passcode guess counting, AES 256 bulk encryption, protection of the AES key by passcode and HW and deletion of the AES key if guesses exceed some threshold. The only real difference is that the key protection in Apple is tied into the HW UID and the key protection in the device pictured is via epoxy that precludes extracting the memory (can't really fill an iPhone full of epoxy).
But back to the issue of war, specifically cyber war. The iPhone is already a defensive weapon that can be used for defense by either side. The occasional dead terrorist's phone is a triviality compared to that. We know that live device use (and live terrorist device use) has no provable protection against attack, so that is where law enforcement must work. Specifically the FBI must mend the bridge to Apple.
For their part Apple must continue to improve their data-at-rest to completely preclude the data-at-rest attack, because if they don't someone else will. If someone else is a company in China and Apple is crippled by a court or legal mandate that will be very bad. The only legitimate manmade would be legal but hopefully Congress will have learned from the Clipper chip and the export ban fiascos.