Answer:
By teaching that if you don't believe, you should die. Look at Islam - either you believe, or you are an infidel, and should die, hence the 9/11 attack on New York and subsequent attacks in Spain and England, as well as the wars prior to the Crusades.
In Christianty, they are taught that the only way to heaven is through Christ, but in a difference from many religions, they are also taught that all are created in God's image, and it is not for us to know or decide who will be saved, so all are to be loved, taught, and cared for, like in the story of the good Samaritan - the one who showed compassion to the non-believer was the one who was praised. So we are not to hate or discriminate against others, but to show them God's love and pray and work that they may come to believe also. Much more tolerant!