Our morality comes from our feelings and our beliefs. Without feelings and beliefs, nothing is wrong. We may add reason on top of that, but you can't ground morality in pure reason. This is why philosophers who reject tradition, and moral intuitions, keep coming back to defending paedophilia. "Yes, but why is it wrong"... is a great line of questioning, but ultimately the answer is "because I feel that it is". Very few people actually want to live in a society where feelings and beliefs aren't imposed on other people with criminal penalties. Such a society would be a chaotic, amoral, nihilistic mess. The only question is which feelings and which beliefs.