It sounds to me like that user is arguing in bad faith. We know that intelligence agencies attempt to influence online discussions about their own activities; it wouldn't surprise me to find out that they're being paid to post here as part of a US gov disinformation campaign to sway public opinion in favor of NSA. That or they've received all of their education on the subject by the perpetrators.

Either way, it's clear they're not coming from a place of promoting transparency or a critical perspective of the government's actions. There's nothing wrong with being a patriot but this is a conversion about government misbehavior, not a loyalty contest.

It's probably best to just ignore them, which is what I'll be doing going forward.