No, it comes from Narcisuss. The word predates NPD by almost a hundred years.
But even if it did come from NPD, it still an objectively negative trait worthy of admonishment. It's not a slur to describe someone's persistent selfishness as narcissistic. It's the definition of the word.
[Edit] it's as much as a slur as using "psychopath" to describe someone who kills squirrels for fun