Of course it can be unplugged. You can also unplug the whole thing from the wall outlet. That's not the point. The point is it works even when you are not playing games.
Thinking like this is a problem. The question isn't "is it possible for people to X". It's "will average citizens have the knowledge, time, and energy to X".
99% of XBox owners will not physically unplug the XBox every time they are done using it because of hazy privacy concerns. Suggesting that a few people could is worse than doing nothing. Those with the knowledge and skill to understand the problem will be inclined to solve the problem only for themselves. A bunch of others will use the "they could just unplug it" line to blame the average user for being insufficiently dedicated/savvy. It dissipates the energy for solving the problem properly. And if the NSA is using the Kinect cameras, then they'll be perfectly happy with photos of 99% of users.
As an example, consider the iPhone. Smartphones existed before it. But by packaging the tech in a way that anybody could use it, they made smartphones mainstream. If we want to make privacy mainstream, we need to do something similar, not fall back on blame-y non-solutions like telling people to unplug things.
