The argument surrounding encryption, mass surveillance and terrorism is a difficult one, normally invoking some firery passions, invocation of 9/11 and some mild racism. If anyone wants to debate with you, just sit them down in front of this video instead.
The arguments made aren't new or novel, but it's an impressively comprehensive look at a very nuanced subject. On the surface, it makes sense that mass surveillance would help prevent terrorism: in reality, it's a big fat nope. [YouTube]