Not terrible so much as asocial -- he doesn't interact with the Order members, and comments a bit too casually about how things were easier after he invented the mind-control hats. And again, he'd barely met Marshall and didn't really try to get to know him before giving the invite. Possibly he didn't intend to kill Marshall, but take him back as a live specimen of an Earth creature, perhaps . . .

Yep. Rewatching as an adult, it's shocking how much they got away with on the show. Simon's parents . . . *shudder*