--Why doesn't God want Adam and Eve to have knowledge of Good and Evil?
Most likely, he is trying to protect them. He wants them to enjoy their lives without them having to experience or really know about evil. I kind of get upset about this--God gives them free choice, so He is almost setting them up to fail in the first place, especially because he gives them the commandment (along with not eating the fruit of that tree) to multiply and replenish the Earth. Is that possible without becoming moral (which eating the fruit would cause)?
Anyways, this kind of "protection" from knowledge is similar to what is addressed in Areopagitica. Much of the texts that are banned from readers go against the church or are of some heretical nature. The root of the reason of wanting to ban these kinds of works is actually good--to protect people from the evils outside of the church that might make them fall away. We are deprived certain knowledge because it's assumed that we would be unable to handle it without being negatively influenced by the content.
--Choice is taken away when we are unable to actually choose good over evil.
I addressed this in another one of my posts: "No reason or agency is involved when we choose good over evil, simply because evil is not available to us by our mothers." (Obviously, the wording would change with the situation.) Isn't knowing someone is choosing good over evil because they personally rejected evil and chose to be good...as opposed to choosing good because they didn't even know there was another option? How beneficial is censorship in the end? We are "good people" because we were led to it, but is that sincere goodness? Besides, sin still exists, even if the books about it are taken away. You can only be protected so much.