I am not sure I understand their argument. With netflix you are a renter. It is their property why shouldn't they protect it. If they were selling you something then sure it should be freely yours with no DRM. As far as these internet ideals that are violated, well I know copyright infringement drove internet growth for quite a while but I am not sure I would call that an ideal. How about we let consenting adults (legally) exchange information how they like and call that an ideal.
Nobody is arguing they shouldn't be able to protect their business, but the proposed changes to the HTML standard would affect every other business. Their authority to demand technological requirements of other's ends at their own property, and Netflix should have absolutely no ability to impose their business requirements on everybody else.
It isn't just their business, it is a common use case for the web today. Hulu, Amazon, audio guys like spotify and pandora are also doing something that would make use of it.
