I think I didn't communicate well: I am all for forcing game consoles to also open up. If one can argue against walled gardens for mobile devices (and I would), the same argument works for game consoles, too. They're both, at their cores, general purpose computers that just have DRM and restrictive licensing slathered all over them.
Also, why even defend the right of megacorps to lock users in their walled garden? What could society or even you possibly win through this?
I am certainly not opposed to gaming companies opening their SDKs and consoles to hobbyists.