It's not that simple, and here's why:
1) Even IF Apple DID comply, how would the software get updated to the phone? You would have to log into the phone in order to install the software...something they can't do. So how the hell would they even update the phone with the software that would allow them to crack the encryption? They can't.
So what do we do? Well, Apple would release an update to all phones that now has this back door, so it can be used the next time something like this happens. BUT:
2) So let's say that they did manage to do this. The problem now is that iOS is no longer as secure as it once was. You have now created a back door that did not exist before. This means that anyone who has an iPhone is no longer protected. Hackers can, and will, get a hold of this back door and cause havoc on people's phones. So you're saying that we should give up personal protection of our private information. Is that something you really agree with in a society that is constantly having their electronics hacked into? And what is to stop the government from abusing this power? We already know our government wire taps illegally. Do you really trust them to follow all the proper procedures for searching people's personal belongings?
In summary:
~The software can't be pushed to this phone
~It gets pushed to all phones to prevent this problem in the future
~Hackers now have a back door that didn't exist before into your phone
Forcing people to give up their personal protection "for the greater good" is not the American way. It creates a slippery slope that could lead us into a martial law country. Because we know how oh so kind and law abiding the government is. The more personal liberties they can take from us, the more powerful they become, the more they begin to abuse that power.