Many people would even agree to it, when they read, that Al-Baghdadi is using Bitcoins to transfer money to his international fight club and there is a need to change some parts of the code, that is EXCLUSIVELY being used to hunt terrorists. Since I am no terrorist and I have nothing to hide ... go along. I know you are protecting me.
For now I suspect quite a lot of people have used Bitcoin to hide big funds (simplest case would be tax evasion). They are not terrorists.
NSA would have, however, only small additions to have to Bitcoin, since the transfers are already somehow traceable.
Blocking addresses would not do much harm since I am certain that for main transfers the terrorists can just learn easily to always use different addresses.
And actually I feel that Bitcoin is safe from NSA intrusion since they don't have much to gain from it and the costs could be big.