I agree with you on all points! BPD is tied with a hyperactive amygdala in the brain — which also makes people more prone to PTSD. It absolutely is a predisposition and it can even be something like perceived abandonment in childhood being programmed in your permanently. People fail to realize that there is so much diversity in BPD with different subtypes, let alone different aspects to their own personality outside of the BPD and different cultures and life experiences. It even varies a lot between men and women and how it manifests due to cultural and hormonal factors. Most people with BPD are truly good and decent people, but the manipulative or malignant types and histrionic types do push the stigma but also need to be understood from a compassionate standpoint.