Dissimilar Ethics

I just don't see how it's meaningful to say that all people, or even just most people, have the same value system.  Even for very basic things like pain, death, the future existence of humanity, the basic sustainability of the Earth, and being kind to each other, people can have drastically different values relating to these things.  And once you get any more specific than that, opinions are all over the place.

I also don't buy value systems converging due to survival needs, both because a.) different environments can create different survival needs and b.) people can and do act against their own values in situations where survival conflicts with those values.

This is one reason why my position is that there is no such thing as a foolproof method of persuasion, and specifically that having someone agree with you about the facts of the world doesn't necessarily entail that they will agree with you on ethical questions.