"The point is in a group everybody acts pretty much the same, that's kind of how the group holds itself together."
"Everybody?" she said.
"Well, mostly, I said. That's what jails and mental hospitals are for, to keep it that way."
"You think I should be in jail?" she said.
"I think you should try to be more like the rest of us" (25.47).
In this heartbreaking exchange, Leo is explaining to Stargirl why in order for them to stay together, she must change. He doesn't understand that if she does change, they still won't be together because she will not be herself anymore. He'll be dating someone entirely new, and someone profoundly less awesome. Or maybe he does understand, and is too immature to care.