EFF never stated that it was an invalid takedown request, just that they believe that youtube-dl has enough legal uses that they think the takedown request was counterproductive.

Op said "Almost all of the lawyers at HN, and the lawyers at the EFF, and the guy at Popehat, are all generally in agreement that there was nothing wrong with what the RIAA or what GitHub did"

OP lied. The EFF never said this. I can't find Ken White ("the guy at Popehat") saying anything similar either, but perhaps someone will post a link. And I don't know what "lawyers at HN" he's referring to either.