Onlar müslümanlara hiçbir müslümanın kâfire karşı davranmadığı şekilde davranıyorlar. - They behave towards Muslims in a way in which no Muslim would behave towards an unbeliever.
People who do not believe in a particular religion are sometimes referred to as unbelievers. believer. someone who does not believe in God or a particular religion
A disbeliever; especially, one who does not believe that the Bible is a divine revelation, and holds that Christ was neither a divine nor a supernatural person; an infidel; a freethinker