Digital sampling opinion - huh?

I read the Sixth Circuit's opinion in the Bridgebort Music v. Dimension Films case, and all I can say is: huh? I'm really not sure where to start. The Judges seemed to indulge the temptation of a "bright line rule" that they think will be "easy to enforce" at the expense of following judicial precedent ("First, although we followed no existing judicial precedent, we did not pull this interpretation out of thin air." [p. 17]). My question is, aren't judges supposed to weigh facts of each case and follow judicial precedent? Isn't that we pay them to do?