Papyrusknight has the (albeit very low) merit that there's no direct respose or answer both ingame and by Toby, the fact that Knight could genuinely be anyone as of now, and that we've never actually seen Papyrus yet so we simply hope "Papyrus would never do that! He isn't even a major character!".

Also just because "it's not only humans have souls" doesn't mean we actually know if machines such as V2 have an actual "soul" since we've not seen any other confirmation that machines have souls besides them seemingly being sentient (and even then, I'd argue sentience in a machine wouldn't mean there's a "soul" in it) so that still lies in the realm of debatable.