I asked why it is wrong, he answered "because it is immoral" and I want him to explain why it's immoral, however I assumed (correctly) that explaining to me why it is immoral would entail assuming other moral truths, like how telling me that it's immoral because it violates the rights of others assumes that I believe that people have rights, and since I don't believe that people have rights, in order for "it's immoral because it violates the rights of others" to mean anything you're going to explain why people have rights, which is itself based on moral assumptions etc.

My "point" is that from what I've seen, every moral or ethic bases it's meaning and authority on assumed truth, that "violence is bad" or "people are entitled to freedom" or "people own their bodies" etc. but those so-called truths are nothing more than opinions that can't be demonstrated to be objectively true or untrue (like "is chicken or fish more tasty?" or "do I smell good?") and once someone disagrees with those opinions and demonstrates that they're opinions as opposed to truths, moral codes lose all coherence.

I was curious if someone who holds "normal" moral values could demonstrate to me that they're in some way superior to "abnormal" values or no values at all, that they're more than just taste.