(1) The architecture of the Internet makes it hard to establish who's really talking to who. The path a communication takes is not predictable and the endpoints of a TCP flow do not tell you who the real end to end communicators are.
(2) This means that intelligence agencies cannot rely upon a traditional wiretap infrastructure, which identifies an endpoint to monitor. Instead, they develop technologies to suck in large amounts of traffic for analysis. Many people consider such technologies a threat to individual privacy.
(3) Therefore, in the interests of privacy, we should develop an Internet architecture in which communication endpoints are better-defined, and communication paths are predicable, so that wholesale intelligence gathering is no longer necessary and can be prohibited.
Obviously, I don't believe this argument to be true. There is substantial benefit to having an Internet that does not work like the phone network. But 'any to any' communication is not without its costs either...