I've been reading up on this issue, and, sorry, blightymam, but I no longer agree with you, on substance, not on stance.
FBI want Apple to replace the OS on this phone and only this phone, to allow FBI to crack the passcode and gain access to the data. FBI are then willing to return the iPhone to Apple so that Apple retain control of the OS.
Apple are seeing this process as a precedent of creating a backdoor to anybody's and everybody's similar device, which they are resisting.
A difficult dilemma. If Apple can create the possibility of a backdoor by replacing the OS, then so can anyone else, for good or for bad.
So, simplistically, one could argue that the FBI are only wanting to access this one phone, and for valid reasons.
But if Apple accede to the request, two things will have been established:
1) Apple will have confirmed that it is possible to force a new OS on to an existing locked device. Not what we want to hear!
2) If this precedent is set, then it will be used time and time again, for ever reducing lesser reasons.
If the case goes through all the legal processes to the Supreme Court it will take years, and surely the intelligence will be well past its 'tell-by-date' then.
A new twist, Mr McAfee (of Anti-virus fame) has offered to access the phone for free, (which has been derided by some). But he is running for presidential candidate, so I suspect ulterior motives there.