Remember kids, The Hakurei maiden can survive eating soil and pineaple air meals, but that doesn't mean that she doesn't want something sweet from time to time.
Okay, littering. :P Jeeze. Destruction of private property (since you don't wanna cast the yukkuri as animals, even if Reimu owned them) and vandalism (since they spilled their filling everywhere). Rawr!
Animal abuse is questionable. We're doing the world a service by giving Punishment to those shitbags! In fact, we should be venerated for it.
Well, the Yukkuri didn't SEEM to be shitheads, and didn't do anything to prompt him to hurt them. And, hey, maybe they were her pets, and she's demanding them to pay in food. Or, she just let them hang around, so when they'd die, she would eat the corpses. An effective way of cleaning up and getting food!