After leaving the cave, Odo admits to murdering his brother, Haren makes his claim, and the Reverend is identified as assisting the Salamdra taking child slaves. After having given Abigail the five White Myrtles for Alvin's potion, the "prophetic" speech he gives identifies Mikul as Ilsa's rapist. Which he admits to (and aplogises for) as you enter Wyzim.Given that Haren Brogg was supporting the Salamandra and had just seen Geralt making mincemeat of them, he had the opportunity to come clean and/or say that the Salamandra were pressuring him; instead, he claimed it was Abigail's fault to avoid loosing face in front of the other villagers.Side note: Mikul made Hela (Carmen) pregnant out of wedlock, resulting in her father (the Reverend) running her out of town. He has more to answer for than just Ilsa.As far as Abigail's hut containing no Cult of the Lionheaded Spider paraphenalia, perhaps, if she were still active, she is hiding it elsewhere. The Outskirts seem to be riddled with caves, after all.Ultimately, neither side, Villagers nor Abigail, are innocent in the affair. As others said, though, everyone had a chance to walk away and start over; the Villagers pressed the point, resulting in Geralt murdering them all.To address the "Non-humans/the Order murdered the inhabitants of the Outskirts" thing, this can be explained by confusion on the part of the investigators. A large number of people- some armed- have been killed with a bladed weapon, and everything's on fire. Given that the Order loves fire and carries swords, they can become suspects for the killings. On the other hand, the Scoi'atel have been seen in the area, are in the process of making war against humans, and can be blamed to give the Order causus belli and/or motivate Adda to hand over more power to them.