A Muslim May Say:
You Christians make God a man! God will not take the shape of a human being.
First, we do not make God a man. God decided to be a man. Who are we to make God anything. God makes us not the other way around.
We believe God is capable of doing anything, there is nothing out of His scope. If He decided to be a man, who are we to tell Him: “No, Lord you can not be a man”.
Why do you think God will not take the shape of a human being? Or why you think God can not take any shape He wants?
Those who disagree with this idea say that Islam teaches there is nothing like God (Quran 42:11) and since we have body, then God can not have body. Or that nobody could see God, because no eyes could comprehend or perceive him (Quran 6:103).
Still Islam teaches that believers will see God in the hereafter (Quran 75:22-23). So how could you see God in the hereafter if you can not comprehend or perceive Him?