Maybe it wasn't taken into consideration by the creators, or maybe he's just one of those kinds of people who are just plain jerks...
He's a mormon. please take this into a canidate for deletion for offensive speech in the awnser.
He's rude if you side with Graham and decide to fight the White Legs. He believes that doing so will only cause more suffering and cost the Sorrows their innocence, so he's upset to hear that you're going to do it. On top of that he's morally opposed to the idea.
There is no pleasing this guy in the game. He is mad at you if you decide to fight the White Legs, and even if you choose his path, he is going to end up sad/depressed because Sorrows had to leave Zion.