If someone can't state their point without warping the very language they use to support their point, it makes it very hard to feel like anything they're saying is credible. Example 1: someone is trying to convince me to vote Republican. They go through the Republican platform issue by issue, and compare/contrast it to the Democrats' stand. However, every time they use the word "Democrat" they instead say "Democrap"…
However, I did adopt Stallman's "Copy Restriction" (instead of "Copy Protection") and "Digital Restriction Management" (instead of "Digital Right Management") - because they are a much better description of what the concept actually is for 99% of the people.
I started doing this after I told someone that I will not buy a Depeche Mode CD I wanted and was holding in my hand in the store, because it has copy protection; they looked at me completely puzzled, asking "Why wouldn't you want your copy to be protected?", and a little more inquiry revealed that they believed it was a somehow more robust (by virtue of being "protected") than non-copy protected CDs.
Language is a very potent medium of control. You are, indeed, used by facebook when you interact with it, and introducing it into the language is a way to bring it to the surface. He's not using "useds" to be clever. He's bringing it to the surface. It might look stupid to you, but I assure you that you are not immune to this kind of bias (and neither am I). I know that's why he does that, because I've heard him personally explain that when attending one of his talks.
In fact, if you look at the works of Kahenman & Tversky, you see that equivalent questions worded differently get opposite responses from people who we expect to know better (e.g. doctors, pilots, ...).
Stallman is basically trying to counter the (essentially unlimited) bias that the media has against what he believes, and I don't know of any tool that does that better than the rhetorical device(s) he is using.