People with borderline as a diagnosis are most frequently people who have survived long-term childhood abuse. It is a common abuse tactic for an adult to blame a child for the way the adult treats them, and say things like “well if you didn’t behave this way, I wouldn’t have had to punish you” and such things. Or to, when the child says something isn’t fair, go off on a guilt trip (“I’m trying my best! You just hate me I’m the worst parent ever I should just kill myself and then you’ll finally be happy!”) to get the child to stop trying to fight back and focus instead on comforting the abuser.
Some children take this mindset and internalize it, and then when they grow up they realize “No that stuff wasn’t my fault, I was innocent” but then take it a step too far with “Nothing is ever my fault, I’m always innocent” and then get into relationships. But we learn all our behavior from the world around us. So if someone grew up learning that as a method of conflict resolution, that might be what they default to in conflicts. And they have the mental protection they built for themselves of “remember it isn’t your fault you didn’t do anything wrong you’re a good person” so they don’t think critically about their own behavior, and will even misremember how things happened. And that’s how abuse is often cyclical. It takes a lot of hard work and access to mental health resources to unlearn that behavior.
I could go on a longer discussion about this. I don’t want to derail your thread, but if you want to talk more about it you can PM me