Finn wasn't feeling confident. It was time for them to leave Era, and after all his talk about change and growth, he decided he'd begin feeling it out. He was done with doing what other people had told him was good and evil. He was just going to listen to his own heart, do what he felt was best. Arbitrary definitions only lasted as long as the people who supported them. If Finn had the power to follow his own dreams, why would he care about those one sided ideals?
"Finn, you're my little brother. I support you no matter what. You're a good guy. That doesn't change because you do stuff some people do or don't like. Everyone is good. And everyone is bad. Like pickles. It all depends on who's chewing."
Yeah... Jake was right. With that decided, they arrived in Magnolia.