What advice could one give that wasn't dangerous?
[1] At least by an adversary with sufficient resources, leverage, and impunity (NSA, GCHQ, etc.)
This war really has little to do with find the way into a named person's communications; it has much more to do with finding the names of people whose communications they want to see.
For that, iMessage is devastating (assuming it is implemented and behaves as marketed, a pretty big assumption).
This is completely false. Use good cryptography properly, and make sure your system isn't hackable. PGP + Tails is a popular combination for Glenn Greenwald and others like him.
There are just too many layers of abstraction to exploit to say a system isn't hackable.
And in a lot of countries you are automatically jailed for not handing over your encryption keys when asked.
Not automatically jailed, but can be jailed when they want the key and not turned over.