You're changing your statement a little bit. "Untreated mental illness" is much broader and more vague than pointing to BPD in particular, and likewise, "bad decisions" is also a pretty forgiving label to place on actively believing hateful things about a racial minority. What you specifically suggested was that BPD can contribute to someone holding racist beliefs, which, unless you have some kind of legitimate research on that, is a little bit of a stretch and potentially infantilizing to those who live with BPD. West is most certainly a mentally ill person divorced from reality, but suggesting that that's what BPD does to a person sounds... not true