>characters don't have arcs
>Bro was evil
>Mom did nothing wrong

Why do you guys feel that just because a character in a story has an opinion that it has to be right? Dave tells Rose that people don't have arcs to calm her down, despite the fact that he himself is a character in a story with an arc.

As for the guardians, Dave feels a certain way about Bro and his upbringing, and Rose feels another. Nothing is stopping you from coming to a different conclusion about their parents than they did. And you take it farther than the characters do, anyway. Bro wasn't evil, he didn't beat Dave or intentionally cause harm, he was kind of a fucked up guy that had no business raising a kid.