What you said is clearly correct, but I don't think it's reasonable to expect any company to insert themselves in the middle of these disputes. At scale it's impossible.
Imagine you run a forum with millions of members and tens of thousands of posts per day. You get a stack of DMCA takedown requests every day. Do you think it's feasible for you to scrutinize each and every one, and take a moral stand on those you deem 'not procedurally valid' ? How much do you think that might cost? What happens when you call one wrong and the law comes to YOU?
For anything to really change, it's clear someone will have to go after the RIAA.. (EFF maybe?)