I think it's less about nice and more to do with self awareness.

The vast majority of us will do anything for that 5 minutes of affection- from bending over backwards to self harm and even suicide but some of us are that little bit more aware of the damage we are inflicting on those around us and are therefore better at curbing the more brutal manipulative impulses.

In the end though whatever we're doing we're all doing it for the same reason and there's more than enough BPD hate out there without us hating on ourselves.