I had to chop out a section specifically comparing the Calormenes with Muslims. There are numerous dark-skinned races in the world, not all of whom are Muslim. Not even all Arabic people are Muslim. And there is more evidence that Lewis based the Calormene god Tash on the false gods of the Old Testament, rather than Allah. If one reads the epic books the Arabian Nights and the Shahnama, I think they will find rather close resemblances between the characters/styles and the Calormenes.