Well, the rabbit is described as our universe, pulled out of a magician's hat, where the magician is God. Philosophers, discoverers, they are the ones Sophie says built the Tower of Babel, or climbed to the tip of the rabbit's hairs. She thus represents the Tower of Babel as a great achievement.
Sophie then represents God, or the magician, as wishing to not reveal the trick, limiting the philosophers and humans. The meaning of this could be taken in several ways. First, God can be seen as a harsh God from this picture - one who limits the explorers, the most creative, wishing humans to live a passive life, accepting their world as it is.
Second, God can be seen as a God who wishes to preserve the questions, and wait to reveal them at a later time - that is, He is not ready to reveal the answers, so He stops the humans from climbing out to watch.
Third, God can be seen as protective - perhaps humans are not ready, or never will be ready, to see the answers to their deep questions, and so He is protecting them from their own wish. There could of course be other viewpoints I have not thought of, but these are the three big ones that immediately appear to my mind.
These viewpoints range from "good" to "bad" - the third viewpoint representing a "good" God, the second not as obviously benevolent, though He could be; we don't know, and the first "bad". The question is which Sophie takes to be the case.
Originally, I thought the first interpretation was most likely, but after more thought, I am leaning towards the second interpretation. The reason is the amount Sophie swings around between different viewpoints on God. At first she questions the existence of God (how could God have come to be?) and then later feels "at one" with God/the universe. Her perspective on God varies as much as that of the philosophers. The second viewpoint seems neither good nor bad from our limited perspective, which makes me think it's the viewpoint she'd take.