Even if you put nothing in his sack, or put a rock in there painted up cruelly as an apricot, and then slammed the door in his face, Spongebob would find a way to interpret the experience as having been beneficial to him, and not just marginally beneficial but tremendously so - as some kind of veritable bonanza of good fortune. Even if you stole his sack from him, ate all his candy, and chased him off with a shotgun into heavy boulevard traffic, he'd never sneak back and set fire to a paperbag of dog poop and put it on your porch and ring the doorbell. Such retaliation would be forgivable, even applaudable - certainly it wouldn't amount even to petty evil, but still it's far far beyond the Spongebob threshold of mean. Quayle, by comparison, might have litmused as mephistophelean. But with these guys, even just looking at the masks you could see they simply didn't have the capacity.
Evil takes some doing.
You have to work at it. You can't just will it and allow it to slither up out of your heart. And just as Kirekegaard thought people no longer capable of sin, so this element has lost its menace. Even the foreign ones.