I wouldn't have a problem with DRM, per say. I think it's a bit anti-social, but it's not a terrible thing. Sort of acting like having a kid that won't shut up in a restaurant.
The problem with DRM is the legal baggage. Specifically DMCA. What we don't want is ending up with a situation were it becomes illegal to modify the functionality of something on Linux because it breaks somebody's craptastic DRM implementation.
Which is what already has happened with DVDs and Bluerays as well as having a dramatic negative effect on efforts to write open source drivers.