"I mean I can't take sides. It'd be a lot easier if I could be I see both sides. (12.51)
Pony and Darry learn what a terrible position they're putting Soda in, always asking him to choose between them. We can dominate people by the choices we ask them to make. If the choices aren't fair, somebody will get hurt.
Darry and I would probably still have misunderstandings – we were too different not to – but no more fights. We couldn't do anything to hurt Soda. (12.57)
Instead of blindly thrashing out at each other, Darry and Pony make a conscious decision not to fight. They are motivated by Soda's needs, but the choice will ultimately benefit all of them.