What matters is relative to one's perspective. Nothing objectively matters.
Nobody's saying everyone is of equal value, they're saying that reducing your perception of somebody into a 2-dimensional caricature because you don't perceive value in them is the type of disgusting mental habit of somebody who either has no real friends or soon will have none.
Have you ever said about someone, "that guy's an asshole"?
If so, you reduced them into a caricature, and you should have instead said "that guy behaved in the manner of an asshole, though I trust that he is otherwise a fully-actualized individual with a life of his own, and with factors outside my visibility that impact his decisions and behaviors."
If everyone matters the same, no one matters.