I know not everyone has poor parental relationships. As I said "a lot of young people" — instead of just "young people" — do, though. I think people who had good parental relationships are better equipped to deal with the crap-fest minority of horrible people in the world.
I mean, maybe one in ten people you meet personally are actually horrible. But, they aren't shy about being horrible. It seems like they go out of their way to be as horrible to as many people as they can in a day.
When you had a great family relationship, it's probably easier to not let the horrible people make you doubt yourself or believe their crap. When you're raised by horrible people, you grow up thinking it's you – because they've groomed you to think you're the reason they're horrible, that you deserve to be treated horribly.
They also groom you to enable their horribleness. Horrible people get away with being horrible because enablers make space for it. And, enablers are taught to enable. I know from experience that it's incredibly difficult to break that programming.