I have always asked people when sprouting off about their rights, "Will you defend the rights of those whom you despise?". If they answer "no" they have no cause to have any rights themselves. Either rights apply universally or they are not rights.
Bear in mind, and this case is an excellent example, rights are about curbing the power of the executive against the people.
As there is already precedent and a constitutional bar (in the US) to demanding knowledge with which to prosecute someone, a rule which has been used by presidents to avoid prosecution, there is no ground to demand decryption keys to open the files.
The government always uses emotional cases to bring about changes in the law which they know are controversial. Mainly targeted at free speech, by using the pornography industry as an example. This is despite the US constitution denying them the power to introduce such laws.
If you hear a politician claiming to be "protecting our children" you can safely bet that is the last thing on his mind. What is really wanted is to make gaining convictions easier, which is a step in the wrong direction. Somewhat like Tony Bliar attempting to remove the right to a jury trial.
When they came for animal rights protester, I did nothing, because I was not an animal rights protester. When they came for the paedophiles, I did nothing because I was not a paedophile. When they came for the muslims, I did nothing because I am not a muslim.
Rights are worth defending, even for those whom you despise. Permitting the government to remove YOUR rights because you don't like someone is just plain stupid. Once lost, they are a bugger to get back. There is never any greater good, and it is often used by religious nuts (George Bush & Tony Bliar) to force therio private agenda on unsuspecting others.
Enough have been removed under fraudulent pretexts, stop it now.