A third possibility... (Score 1)

in addition to a) cynicism, and b) ambition, is c) a genuine dislike for the might-makes-right tactics of the RIAA, coupled with the ability (being a licensed attorney) to actually do something about it.

Unlikely as it may sound, there are quite a few lawyers out there who actually have principles and respect for the rule of law. It's entirely reasonable to think that they would dislike seeing the system gamed by the RIAA in this way. Time and events will be the ultimate proof, but don't discount the possibility this fellow is motivated, at least in part, by principled indignation.