After two seasons, qw still don't know a ton about Moose — which means he could be hiding something. If Moose is upset enough over Midge's senseless murder last season, he could take on a vigilante-justice type of role as the town's next villain. It's not clear why he'd target Dilton and Ben, but maybe the ritual isn't meant to kill them. If Moose (or another student) needs supporters his own age, the two of them wouldn't arouse suspicion, since they're not close friends with any of the show's main characters.