I, for one, can completely understand the feelings of frustration behind the statement. Also note how forcefully arguing positions managed to derail the entire thread above into unnecessary bickering about what basically amounts to a matter of nuance (as happens so often in discussions about NSA scandals, hence the frustrations), while this cheap shot, in fact, did not. Quality of discussion, you be the judge.
I get your point about remaining civil (though I disagree that stooping to lower levels always weakens one's arguments), and I commend you for taking such a proactive role in this, I really do. Sometimes though, discourse here has different problems than strictly has to do with civility, when I open a thread about yet another NSA scandal and I see tptacek pushing the very same hot button again and again, derailing all top discussion into something that has little if anything to do with the topic. Yes sure he is often technically correct, but he's a smart guy (really smart, and that is when I'd expect better, wouldn't you?), knowing very well that what and how he writes makes people think he's defending the NSA somehow. Somebody will engage, and the by now very familiar pattern unrolls in the same way it always does, taking up parts of the thread-space that could've been useful and interesting discussion. He could also make the same statement in a much less inflammatory way. Or simply not at all, because in this particular case he was pre-empting a sentiment that nobody actually claimed.
In short, I don't think forcefully arguing their positions would have addressed the frustrations that gave cause to coldtea's "cheap shot" (I can't really speak for him of course), but rather the opposite.