You were a religious person. You went to church, had beliefs that Donnie thought were stupid. But he restrained himself as much as possible. Doesn't mean he succeeded.

One day, Donnie thought he'd tag along to see what church was like. "Oh GOODIE! Worshiping a magical being that we can't even see!" Donnie tried to be supportive, but it just sounded sarcastic. It wasn't intentional.