The noted free software activist has come out against Steam for Linux, writing that: “Nonfree game programs (like other nonfree programs) are unethical because they deny freedom to their users. (Game art is a different issue, because it isn’t software). If you want freedom, one requisite for it is not having nonfree programs on your computer.”
It’s the argument I would have accepted from Stallman, actually. But that doesn’t mean it’s necessarily right – or the best one he could have made.