While I agree with you on that fact that I do not support other people posting content that someone else makes, I do not believe the way is through Dtube blocking the users from uploading. It is up to us as users to self regulate the system and down vote/flag those videos, if you are against them. Going to dig deeper into the question form a legal standpoint and try and come up with some better answers to our question here.
RE: Very Serious Question FOR DTube & Steemit - Posting Mainstream Media Content on DTube?