So Catholicism of the Middle Ages was not a religion?
I understand and in general agree with your point. But it is much more accurate to say that Islam is not JUST a religion, in the way others are. It is a political/religious/cultural amalgam. This does not make it any less a religion, though.
Also, technically speaking, Islam does not call for the death of non-believers, at least among People of the Book. They do, however, have to accept submission to Muslim rule. :)