But that's not what Stallman believes, that's what the author of the article wrote. What makes a freedom a freedom (to me) is that you have the ability to waive a freedom if you wish to do so -- otherwise it's an obligation. And Stallman is of the opinion that you should never trade freedom (at least when it comes to proprietary software) for convenience. I actually asked him about this a few weeks back, if he thought there were situations where it's reasonable to willingly and in full knowledge give up some freedom (the question was in the context of software as a service). He interrupted me before I finished and said that you should never do that, because even if you're not giving up much freedom now, they'll be taking more and more of it as times goes on. (I hope I'm not misrepresenting his views, but that is the impression I got.)

I disagree. While perhaps it's wrong that many people give up freedom without really knowing that they're doing so, I think it's reasonable to on occasion to do it if you know the trade-off you're making.