We should keep in mind that this is a myth. You may take what message from it you like, I suppose. I'm sure there's more than one thread of meaning in there. I agree that it wasn't about 'knowledge' in general at all. It was about 'the knowledge of good and evil' and our inability to judge good and evil because of our limited mortal understanding. (This aligns with the later observations that 'we know not what we do', 'judge not, that ye be not judged', etc.) Thus the stricture enjoining them to not eat of that fruit, eh? If it was about obedience and control, any kind of tree would do for the story, I would think...the tree of really tasty cookies perhaps...'Don't touch' thunders God. 'Those are my cookies!' Instead, the tale specifically refers to the knowledge of good and evil. Every time we declare an enemy to be evil, as they declare us to be, we taste that fruit: war and conflict and the loss of paradise.