It is true (independently of our conceptualisation) that it is wrong to inflict pain on a sentient creature for no reason (she doesn't deserve it, I haven't promised to do it, it is not helpful to this creature or to anyone else if I do it, and so forth). But if this is a truth, existing independently of our conceptualisation, then at least one moral fact (this one) exists and moral realism is true. We have to accept this, I submit, unless we can find strong reasons to think otherwise.