Didn't stop him from making the one Grail agent stay on a beach until he counted a million grains of sand. Although he only did that because the guy kidnapped his girlfriend. Or the guy he made to literally eat his gun (cut to a shot of the guy and his bloody mouth with teeth fragments hanging out, trying to bite…

If it's anything like the comics, it's not so much a possession (cause Jesse is always in full control) as the being just gives him the purple man powers. As far as Jesse's morality and raison d'tere goes, it can pretty much be summed up with this Bill Hicks quote, which I believe appeared in one of the issues:

Plus, his name was Stratton, which was Tim Matheson's(the bad guy from Fletch) last name in Animal House.