Despite what some on the political spectrum try to say, the Internet has become a basic human right. It is required in schools in America. In many cases, it is required to even interact with certain government entities. Allowing governments and corporations to force users to a specific browser on a specific operating system just to interact with their site goes against everything the web is supposed to be -- an open platform for the free exchange of ideas.
This proposal is a slap in the face to all of that and basically allows governments and corporations to force users to use what those governments and corporations choose.
This is net neutrality all over again, just in a different vein.
I, for one, will continue supporting Mozilla and Firefox and will never again use Chromium-based browsers, or any browser which supports this. I just hope I can keep browsing the sites I need to.