Total bullshit. If people start shooting and bombing, then you pick up your weapons and you kill them.

You don't get to mass "scrutinize" random citizens by eavesdropping on their private communications just because terrorists might be hiding among them. If you do this, you are the terrorist and anyone who resists you has the moral high ground. Cryptography and anonymization technology are merely one of many forms of self-defense against your tyranny.