But how does it make sense for them to be held responsible for an action they didn't know was wrong?
Whoa there, you are overthinking this...
What did God tell them to do?
Gen 2:16 And the LORD God commanded the man, saying, Of every tree of the garden thou mayest freely eat:
Gen 2:17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.
Did they clearly understand it?
Gen 3:2 And the woman said unto the serpent, We may eat of the fruit of the trees of the garden:
Gen 3:3 But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die.
So what happened?
Gen 3:4 And the serpent said unto the woman, Ye shall not surely die:
Gen 3:5 For God doth know that in the day ye eat thereof, then your eyes shall be opened, and ye shall be as gods, knowing good and evil.
Gen 3:6 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.
She allowed Satan to cast doubt on what God said and they disobeyed the clear teaching of God.
You realize that he has done that ever since, don't you...
Rev 12:9 And the great dragon was cast out, that old serpent, called the Devil, and Satan,
which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.