I don't think we're disagreeing on that point. All I'm saying is that the nature of the hash as being derived from the movie file is irrelevant. If people organized movie torrenting by assigning version 4 UUIDs to movie files, then Popcorn Time would infringe just as much by publishing those UUIDs as it does by publishing hashes. There's no "derivative work" argument being made on either side. If there was, the pro-Popcorn-Time side would win.
Clearly some uses of a Hash qualify for fair use, but it’s hard to argue that Popcorn Time is one of them.