Should you argue about morality with someone that doesn’t believe in Morality?
if you ever meet up with someone who holds to the philosophical idea that we don’t really exist except in our mind (like the ideas of George Berkeley) – what point is there in even arguing (except for sophistry which is indeed fun).
In the same vein, if you find someone that doesn’t believe in a standard of morality they have nothing to offer in any discussions on morality, for all they can offer is the idea that there is no such thing as a standard for morality; which is indeed a statement of a standard for morality, and therefore it is self-defeating.
It’s like saying out loud "There is no such thing as sound"…