The ‘big guy in the sky’ gave us ‘free will’ aka the power of ‘freedom of choice’. The knowledge of the difference between good and evil helps us to make those choices.
If we choose to honor God's will, then our choices will bear fruit. If they do not, then we garner a pocketful of brambles. Judge the tree by the fruit it bears. The choice is ours. You can, if you desire, choose to go your own merry way without considering possible consequences (Cosmic Law of Cause and Effect), but you will reap what you sow.
If the only way a person can believe in God the Creator is to take the Bible literally, then I suppose that's better than no faith at all. However, once you begin to understand the deeper meanings of Jesus' parables, then you're ready to begin to understand the allegory about the Garden of Eden and the “Tree of Knowledge of Good and Evil”.