It's up to the end user - if the GNU movement is somehow planning on restricting the ability of the user to use DRM'd software on their own systems, then they've gone completely off the rails.
Where in that did you see him advocating preventing the user from installing Steam? He's just saying that installing proprietary, DRM'd software reduces your freedom; so if you want to promote freedom, you shouldn't install that software on your computer.
One thing to keep in mind is that most of the time, he doesn't want to force anyone to do anything (other than make sure that code free if it was written under the GPL, even when modifications are made). He just suggests that people who value freedom do or don't do certain things.
Nowhere does GNU or the FSF advocate preventing the user from doing as they please; the user is more than welcome to use a DRM-infected system if they choose to do so.
