Youtube-dl had some good notes in their README about legitimate uses and an explanation about how they tried to avoid adding sites that specialized in infringing content, but they really did themselves a legal disservice by explicitly using copyrighted music video content as tests. That will not help their argument at all. Youtube-dl absolutely has important and completely legal uses, reporting being among them, but…
The first two elements have a mens rea implication behind them: you have to demonstrate the intent of the developers. That RIAA's strongest evidence of intent is buried in a unit test, and this seeming intent flies against the evidence in the far more prominent README that is discussing its unsuitability for infringing content. Furthermore, they can also demonstrate from their own practice in history that they refuse pull requests and close issues were people are clearly trying to use it only for infringing use cases.