Sound like a reasonable objection? At first glance it might. It seems to be asking me to speak more understandably using just words we both understand.
But hold up a moment. How does this similar objection sound?
It's absurd, isn't it? I may be an atheist, but of course I can talk to theists, and understand much of what they say about God. I can even talk about God myself, and sometimes do. (I dare you to say, "Oh my God! You're such a hypocrite.)
And furthermore, suppose I had no notion what God meant, and couldn't understand anything to do with him. On what basis, then, could I assert that God did not exist? Don't I need to understand what God is to be sure he's not real?
Well, everything I've just said about God makes a perfect parallel for the Good and Evil case.