If someone insisted that the NAP *is* morality and that any other definition of morality is wrong, what do you do?

Obviously the standard reducto ad absurdium(what if you had to use force for the ultimate good) won't work as force is always wrong and there are no situations where it's right in their view point.

Do you try to point out the tautology, or do you just give up and try to prevent their ideas from spreading?