Borderline personality disorder (BPD) has a bad reputation, and its diagnostic criteria are notably vague. In this chapter, we focus on the “inappropriate anger criterion” and highlight different ways of understanding it considering philosophical accounts of the nature of anger. We submit that the openness of the criterion heightens the risk that patients’ anger is assumed to be unreasonable in a way that disrespects their moral standing. We tentatively analyze this situation as one of testimonial injustice, where negative prejudices about a bearer’s identity lead interlocutors to deflate the bearer’s credibility. Although this captures part of the picture, it does not capture all of it. We propose that the case at hand often also involves affective injustice, broadly defined as a wrong done to someone in their capacity as an affective being. The injustice here is typically the injustice of unjustifiably dismissing BPD patients’ anger as merely symptomatic of an underlying pathology and not fitting given the way they are being treated or, more generally, given their situation. Plausibly, persistent exposure to this kind of injustice can undermine patients’ moral agency when they internalize the disrespectful idea that they are unable to experience justified anger in response to moral offense.