I think, as a society, it boils down to this: "And while the government may argue that its use would be limited to this case, there is no way to guarantee such control." Can a private, for profit, company deny the will of an elected government working to solve a heinous crime based not on what they say they will do but because they cannot give a 100% guarantee that this is the only time/way it'll be used? Apple ackno…
But Apple isn't saying they wont do it. They just want to make it really clear that they're not happy about it and they want the government to change their mind.
The government still has a monopoly on the legitimate use of force.