The story is even worse then that. God provided the tree of knowledge, and instructed man not to eat. But man did not know of sin yet. So Gods instruction had no depth to it. When Satan came along and said that it was ok to eat from the tree his instruction now overwrites God's. Again, because man had no way to determine right from wrong. It was only after eating from the tree of knowledge that man was "gifted" with the ability to know right and wrong. God still gave man eternal punishment and used that single event to make mans life full of eternal suffering.

Even a "simple" creature like a human can see that man was not competent when he committed the crime. God was unjust in holding man accountable and giving him the the equivalent of life in prison with no chance of probation.

This is all told in Genesis 2 & 3. It's very simple to follow. Man did not have the ability to understand right from wrong BEFORE he ate from the tree of knowledge. Yet God punished him for eating from the tree. God was unjust. Man was innocent.