All he has to make sure he understands is that creating a backdoor to iOS devices will make every iOS device the government and its security agencies are using instantly hackable. Even in the simple case of losing or forgetting a phone belonging to a government official in a taxi, at an airport, etc., will immediately become a possible exposure for national security. His national security crowd's phones will be the most desirable hardware to conduct espionage against the US.
What the FBI ad DOJ, as well as some nimrods in Congress are asking for is tantamount to not only a threat to everyone's privacy and safety, but a serious threat to national security. And all of that because the FBI was ignorant on technology, and furthermore was stupid enough not to talk to Apple BEFORE changing that password!!!