The argument about criminals going dark with crypto is just fear bating and FUD. The criminals you "really" want to worry about are already dark. The only people iOS8 protects are your standard domestic criminals, which if they hadn't already learned how to use crypto trust me --- they likely leak like a sieve through many other vectors (web mail, pc's, ISP, etc).

What we should be debating is job security for domestic police. Because if we do not put user-centric-crypto in everything one day police will loose their jobs to robots and algorithms. Well, at least this argument is only as absurd as the authors FUD.