Before eating the forbidden fruit, Adam and Eve either knew that disobeying God was evil or they didn’t. If they didn’t, then they can’t be blamed for disobeying him. If they did, then they already possessed the knowledge that God had forbidden. Either way, God could not justly banish them from Eden. (Adduced by Richard R. La Croix.) Link.
Adam knew that disobeying God was wrong. He knew shouldn't do it. You don't need to understand a command to obey it. Would you take that excuse from a child? Why would anyone think that it would fly ever? No way would my parents buy that. No parent would. Go back and read Genesis 3. The knowledge was not forbidden - eating the fruit was.
Debunking Christianity: Adam and Eve Again