I think the more interesting question on this topic is whether and when calling people narcissistic is fine or not. Is it a slur? I don't think so. Is it an insult? I certainly don't think it categorically and always is. It depends on context.
Identity... wasn't it a "gender" a moment ago? As in, "don't misgender"? 🙄
Neither autist, nor homosexual, nor narcissist are slurs. If we look at other "marginalising" words, there are some more non-slurs like: rapist, murderer, felon, poor, ugly... etc.
Tough luck, but being NPD doesn't get a pass at claiming it neither a gender, nor a slur. Its socially negative nature also doesn't get a pass at embracing it instead of trying to change. The onus is not on society's end with this one.
(PS: as a "PD cluster A, B, and C, on the spectrum, others pending", NPD is like "that's all?" 😆😐)
Bold claims for an article claiming to discuss psychology, without any peer-reviewed scientific sources. Then again, psychology is only half-science... but still.