‘A Jewish killer is a killer, but first of all a Jew, and so he will benefit from God’s mercy more than any Gentile’, this is a paraphrase of a saying attributed to a rabbi from the first centuries of the Common Era.
Disregarding the doctrine about the chosen people of Israel, it hints at the deep feeling of fraternity between the members of the same religion. Surely, it also seems to be a discriminatory judgment, but the strong reliance on the same god is in fact its core.
The secular humanism has not been able to produce the same feeling of brotherhood, firstly because it cannot be present in the key moments of the human life like religion. For instance, it is really hard to die in humanistic terms. Second, because it has sustained a doctrine of individual freedom which has led to the formation of many separate communities.
The members of the same religion know that they are born receiving the same rituals, that they often solve their problems by appealing to the same god, and that they will die with the same hopes into an eternal life and will be buried in the same way.
Such similarities can make an individual to sympathize with a bad member of its religious community more than with a good member of another community. Such kind of sympathy does not involve that the bad purposes of the bad member are shared by the entire community, even if he would claim a religious motivation. That feeling is based on positive similarities; it cannot inspire an evil brotherhood. And it is a human feeling flourishing in the religious communities, so that it cannot prove to be negative into a religion or another.
The path from sympathy to the hatred against ‘Gentiles’ cannot be derived from the sympathy itself, but only from the outer attacks on the whole brotherhood of coreligionists.