As a defender of Ghirahim, I'd be remiss if I didn't defend the demon race as a whole. I'm not saying they were all good, (Demise certainly wasn't) I'm simply saying that they are a species like any other of the setting and I'd prefer they were treated with the same nuance.
That being said, I really, really, really do not like the Batreaux side quest. The only unambiguously good demon in the franchise so far, and his storyline involves changing his very species just so he can fit in.
Which is absolutely horrifying if you stop and think about it. Link is turned into a hylian savior, and Batreaux is made to feel bad and hate pretty much everything about himself because of the actions of others.
Kukiel had the right idea. She always accepted Batreaux for who he is, and says that she misses his flappy bat wings when he becomes human. Speaking of which, how is Batreaux meant to participate in the Skyloftian community now? He's lost his wings, and he's never seen getting a loftwing. If it's not his demonic origins preventing him, it'd be that the goddess statue was used to make Imprisoned pancakes so can no longer be used for the coming of age ceremony.
Seriously, what message does this send? Some kinds of people are just bad and have to change everything about themselves, discarding their entire culture and identity just to be not treated like monsters?