Okay first of all when google tries to eliminate child porn, they have the assistance of the police who in general are trying their best to eliminate this content because we've deemed this sort of content less than legal. I think most would agree this is a clean directive and relatively simple to understand.
When it comes to media organizations such as RIAA, it's pretty obvious they don't care too much about the music, people or privacy. All they care about is making money from the system. This results in them blanketing everyone with lawsuits including themselves and folks who are completely innocent.
If the police were like this it would be like them shooting everyone in the building to catch a single criminal because somehow that's a much better idea that actually doing your job correctly. This is the key difference between google looking for child porn and looking for pirated media. The organizations they need to co-operate with operate entirely differently.