It's an argument about internal consistency, it seems. For a moment, grant all the premises, suspend disbelief, and just read it as if it were a history book.
"The man has now become like one of us, knowing good and evil."
So, before eating the fruit, neither of them "knew", or "understood" good from evil. I think that it is safe to say that anyone that doesn't understand a distinction between "good" and "evil", doesn't know "right" from "wrong".
Assume God had many discussions with Adam about what to do, and what not to do. No matter what God said, Adam was incapable of understanding why he would refrain from any act at all.
For example, what's an "evil" act? What if someone were to violently torture and rape a baby? Seem pretty evil. Can you imagine being truthfully confused by the statement "you should not rape and torture a baby because it's wrong, its evil"?
Adam and Eve were basically psychopathic postmodernists.
In legal terms, Adam and Eve were not capable of having the mens rea to commit any "crime". They cant understand "crime" itself.
In short: By what mechanism did God expect Adam and Eve to do "the right thing"? And for what reason is the ultimate price appropriate or justified?