Because it completely turns a lot of our societies meta-narratives inside-out. One of them being that humans are born equal, how can we believe that we are created equally by a common creator if now some are being created to be "better" than everyone else?

Is there a point where we end up creating someone that isn't human? If they aren't human, what kind of rights are they to have? So many weird questions that we don't exactly have the answers ready at hand.