What is wrong with the Muslim belief of a sole, transcendental God that is the sole supreme creator?
That's not just a Muslim belief. Some polytheistic faiths have a sole supreme creator God or Goddesses - and then lots of other Gods and Goddesses.
What's wrong with teaching, a supreme God, monotheism?
What's wrong with teaching, a supreme race, racism?
While this comparison may seem to your typical theist as trite, try and remember the history of people confusing Jew with race, religious belief with race.
(incidentally that's another wonderful example of how most people believe what they are taught to believe - so much so people begin to confuse religion with "race").
Why are these beliefs wrong? They are wrong because we live in a world with many different races. It's not good to teach children that there is only one Supreme Race. We live in a world with many different Gods. It's not good to teach children there is only one Supreme God. These ideas (memes) are successful because they connect us with a ancient tribal identity, something that was important to the success of our species long long ago. We don't live and kill as if we were living in the Stone Age or even the Bronze Age (well some of us). It's time we socially progress past these Stone/Bronze Age memes.
Actually, thank the Gods, many of us have