This isn't quite the same as that old "well, just don't use it" canard.
Valve was engaging in a set of behaviors which you considered acceptable, and so "purchased" (more on why "purchased" is in quotes in a second) some games from them.
They've changed their behavior. Let's say you don't want to do business with them anymore. You could, of course, stop using Steam ... and lose access to all your games, which you probably thought you "purchased" in some sort of "I can use it for the rest of my life" sense, but actually just got a license to use for as long as they feel like it. This is different from a "service" where the expectation is that the benefit you're getting from them is recurring on some sort of cycle.
Someone will, doubtlessly, point out that you can put the Steam client into offline mode. To which I'll say that you can't do it indefinitely. To which they'll say "but Valve says you should be able to do that," to which I'll point to http://www.pcgamer.com/2013/11... which basically says "Valve says they want to make offline mode work 'forever', but they're not there yet."
It doesn't really matter, IMHO, that the scope of what they did here was relatively minor. The issue is that Valve, much like Sony, feels like they can trawl through your computer in areas that have nothing to do with playing the game. Today it was minor because it makes sense to start small; but if they feel comfortable trawling your DNS history -- and Newell clearly says that he has no problem with this practice -- what else do they feel comfortable doing?