Finally, someone with a theology background to discuss with. I really appreciate your answer and the time you took to answer, and if I may I will tack on a few more questions.
Essentially, according to the creation myth, the decision for the apple was not made directly by mankind. Snake came and tempted them. Actually, IIRC Adam himself did not deliberately eat from the forbidden fruit, it was offered to him by Eve and he unknowingly ate it. That does indeed raise a few more questions.
1) Was snake sent by God, did it act on Gods orders, with his blessing, his knowledge or behind his back? The answer to that might seem trivial, unimportant at first, but it does entail a lot of follow up questions.
a) If God's intention was to test his subjects, he might have ordered snake to tempt them. That would make him a highly unfair God, though, since he punished snake for doing what it was told.
b) If not, well, what's snake's motivation? Was snake tricked itself by some other force, an adversary of god, or did that adversary take on the form of snake? You have answered the omniscient part already, so the "why didn't God know" section is answered. But I would expect a God like that to know WHETHER he has some kind of adversary who would try to mess up his experiment. But if we assume that God did not know about his adversary, and considered that snake acted on its own or that the adversary took the form of snake, wouldn't he err when punishing snake? Can God make mistakes? Can God be tricked?
2) Why was Adam punished? It is possible to trick man. We know that much, from experiment and experience. And while I know that it might not be very sensible to apply modern day sentiments towards legality and justice, isn't it highly unfair to punish someone for something he didn't want to do? To a Muslim it is no too big a problem if he happens to eat pork, provided that at the moment of eating it he did not know it was pork, and provided that he stopped the very instant he notices it. God's reaction tells us that he did know about Eve tricking Adam, because her punishment was a lot more severe, but he didn't get off with a swat on the back of his hand either.
I am of course aware that we're dealing with a creation myth, a myth that had an agenda, i.e. explaining why things are the way they are, and also instilling a certain basic respect, if not fear, towards God. That's a given. Still, it should be consistent. Respect towards an entity, being or organization requires that you accept his superiority. And to be granted respect and not merely fear, being "more powerful" does not suffice. You also need to be at the very least as wise, just and knowledgeable as me. Otherwise, you might get my fear, but you may dream of getting my respect.
And I do think the makers of the bible wanted the people to respect God.