It's much dumber even than. A youtube web page contains everything necessary to view a youtube video. The concrete action the RIAA is accusing youtube-dl of is that it "circumvents YouTube’s rolling cipher". The RIAA has used this same complaint to have other sites/tools taken down. I've looked into the youtube-dl implementation, and it turns out the Youtube's "rolling cipher" is at most merely rearranging the characters of the CDN url of the video, and they send you JS code in the page to correctly arrange the characters of the URL so you can download it. Youtube-dl is using the Google-supplied JS and a JS interpreter to transform the Google supplied URL into the URL they need to download the videos. Youtube is asking Google what to do, and Google is saying "here's how you download the video".

I explained the full RIAA complaint, with links to prior complaints and the youtube-dl source code, here: https://news.ycombinator.com/item?id=24874111

IMHO the biggest problem here is the US government is policing the world with DMCA: you have to comply even you are not with physical US jurisdiction. Like the world's biggest cyber-troll, just dressed in business suits.

Copyright lobby has been pushing the line tighter every year, every decade.