I don't mean their appearance, for youthful body can hide a mind far more dangerous than of an adult. I'm basing it on what I know of their behavior towards those they met, as well as what they said.

[After all, he's been investigating it for a long time, and gathering information.]

That's only one side of the coin. The human cultists are the ones appearing each and every time, no matter if it's during a ritual or distributing charms. The cult itself is a purely human organization, where lowest rank has no idea whose orders they follow or which god they pray to. According to them only the initiates know this. [Archer narrows his eyes.] It's the lowest rank of cultists that we've been dealing with. Their methods of communication ensure there's nothing to lead to higher rank, not to mention leader or leaders of this cult. The ofuda are the only tangible link, for the cultists do not make those themselves.

At the same time the cultists believe they have to create new gods that will listen to their prayers, and get rid of the old gods. Who can say that those two gods are the only ones, or aren't a bait to test the Heaven's reaction? In such case killing them means destroying the only possible lead to the real culprit, be it god or a human.