There appears to be an issue with the triggers for dialogue in this quest. Upon learning the truth of matters, it triggers a conversation with Lae'zel who promptly tells me off for accepting a bargain I never accepted. Once I learned the truth I slaughtered the Paladins, I did not accept their quest. This conversation should not be triggering unless you accept the quest to hunt the Devil.
On a side note, upon learning the truth you are not able to challenge the Paladins about it, there is no discussion to be had because no dialogue options show. I don't know if this is a bug or an oversight or plain bad writing but you really should have the option to discuss your findings and challenge them about their folly.
