bpdtards are collectors
they take a person's interests, viewpoints, personality etc as their own and then get rid of them and turn them into fictional characters in their little story. In my dealings with them (multiple) I found that they hate all the people in their pasts and vilify them but also relay these events with a certain fondness or nostalgia and keep momentos to remind them. Not because they care about other people, but some weird reverence and glamourization of their story's narrative.