Chief Rabbi Lord Jonathan Sacks, in his The Dignity of Difference sheds a brilliant light upon the subject of humanity and religion.

One belief more than any other (to quote a phrase of Isaiah Berlin) is responsible for the slaughter of individuals on the altars of the great historical ideals. It is the belief that those who do not share my faith, or my race, or ideology do not share my humnaity. At best they are second-class citizens, At worst they forfeit the sanctity of life itself. They are the unsaved, the unbelievers, the infidel, the unredeemed; ...if faith is what mskes us human, then those who do not share my faith are less than fully human. From this equation flowed the crusades, the inquisitions,the jihads, the pogroms, the blood of human sacrifice through the ages.