This statement is completely irrational, just like Christians who say the Koran is wrong but have not read it carefully. When Muslims say that the Bible has been tampered with, they admit it in disguise. You can only see the surface but not the essence.
No one has really seen the appearance of God. Whether he looks like a man or a dragon is unknown, or whether God can look like a man or a dragon, depending on his own preference.
We knowing God not according to his appearance, but the word of God.