I'm sorry, but that's straight up wrong. The ettin was exactly in keeping with one of the major themes of the comic - the sophistry people will engage in so as to justify themselves when performing actions they know can only lead to a bad end. It's not just a zealot's thing. It's a thing that will come out at any time, often at the worst possible time, and it's not something that can be reasoned with directly. You have to reason around it by appealing to those who are witnesses, if at all possible. The ettin is absolutely engaged in the same game of justifying bad behavior as the Sapphire Guard leadership and everyone else.
I can probably expand on this when I'm not meant to be playing D&D.