Okay, that's Finland, not Sweden, but still Scandinavia.
And now I feel bad for mixing the beautiful, dreamy world of the Moomin Family with something as monstrous as Simon Öhlund. But on the other hand, maybe it's not the Moomins who get corrupted by Simon, but rather the wickedness of Simon is ameliorated by the Moomins. I'm quite positive that ever-gentle, ever-understanding Moominmamma could somehow re-educate Simon into a kind and loving person. And if she cannot, maybe a hearty chomp on Simon's leg by Little My will do the trick.
And if everything fails, the Groke could just freeze him or eat him...