Well people of their own side who think a particular person is crossing the line, should ask him not to do so, or atleast report him.....only this way we can weed out people pointed out by you.
Have rivalry, no problem, do some leg pulling no problem, but one shouldn't comment on someone's religion and sensitive aspects.
Also, it happens that some person unknowingly hurt person of other religion, so its better to tell that person and if he does't stop even then, report him, and mods should ban him.
A mod can moderate posts.. not emotions.