This isn't true unless you limit yourself to key exchanges that are entirely online. Offline key/certificate exchanges will still be resilient to online MITM.

This isn't true unless you limit yourself to key exchanges that are entirely online. Offline key/certificate exchanges will still be resilient to online MITM. Attack vectors on implementation notwithstanding. Of course SSL-type stuff is out. My guess is that many governments have their hands in the CA cookie jar for a long time now.