If the users have a choice to refuse to buy SIM-locked devices, then Nokia has a choice to build such devices or not. In particular, Nokia then has further a choice to spend their dollars on better free software applications, or on DRM infrastructure that allows the proprietary market to enter the platform (they are trying to do both now).
Saying that adding DRM to the platform is necessary to get better games for example is actually quite an insult. Are the available games for GNU/Linux not good enough to attract a large number of people? If games are so important, why does Nokia not spend the millions it costs to develop DRM technology on developing awesome free software games?
Apple found a viable business model with the iphone, and Google (with Android) and Nokia (with Maemo) are now trying to imitate it. That's understandable. I am not sure if that's the only viable strategy for a phone company these days, but let's assume it is necessary. Then Nokia could still communicate these actions in a way that respects what the community decide with regards to DRM in the last decade, and answer the concerns about a deep fork in the code base with regards to the GPLv3.