This whole mess is nothing but political grandstanding. Apple offered to work with them through a FISA court so that all of this would be sealed. The FBI refused and decided to make it public to force a lawsuit. The government already has access to the iCloud data so they basically have access to all of the data on the phone. I don't know if it was a strategy or stupidity, but they changed the iCloud password. If they would have left it alone, they wouldn't need a backdoor into the phone.
Apple is a global company. If they are forced to do this for the US, they will be forced to do it for every other country where they do business. Are we going to be comfortable knowing that China, Russia, and tons of other countries are going to have a key to get into any device they choose. And how long will it be before some criminal organization gets a copy? Law enforcement has plenty of other tools at their disposal. They don't need this. The potential for harm far outweighs any good that could come from it.