That was my point: someone claimed that a special, DRM-enabled "safe browser" would never happen as long as there is open source, and I am saying that no, in fact, open source is not going to save us here. The problem is that there is almost no chance of an open source CDM, and a near-guarantee that proprietary CDMs will dominate. Open source browsers will either capitulate and include DRM, or fail to do so and languish in obscurity as their users find themselves increasingly unable to use the web.
It is not just about Hollywood. The New York Times will use DRM to try to enforce payments. Scientific journals will use DRM to stop people from sharing articles. Photos will be DRM'd by companies that want to force you to go online to view them, to pay extra for setting them as your background, etc. How long do you think Mozilla can hold out against the pressure to include DRM functionality?
So people who choose to use only free software will be excluded from large parts of the web. How is that a good outcome?