There is a kind of sleight of hand at work in this counterargument, which is that nobody is advocating for a secret, extrajudicial, arbitrary set of rules about what is allowed and what isn't. Even if I say I'm OK with the government reading my email, all the work is ahead of them to prove specific charges in a court of law, should I catch their interest. The spy agency does not, in fact, get to decide what's right and wrong. The existence of a surveillance state does not imply the existence of a secret police with extrajudicial powers.
Not sure I see how it's relevant here, since we're granting that the spy agency in this case has every right to gather evidence. The point is that they don't get to unilaterally decide if that evidence constitutes a crime, which is what the original comment suggested.
The first thing that authoritarian and fascist states create is the police with extra judicial powers. Like flies and shit, they are always found together.
