The diversity of the modern world seems to pose a fundamental problem for religion. No matter which religion you are, most people are a different one. As a religious person, you basically need to believe that most of humanity is wrong (as I believe that people of all faiths are wrong). You need to believe that because of the supposed validity of religious truth. Either god exists or he does not; either he wants us to behave in certain ways or he does not.
As such, you can either accept that several faiths are acceptable to god (significantly diminishing the degree to which yours can be considered ‘true’ or special) or you can assert that most people hold faiths unacceptable to god, possibly courting damnation.
The first position demotes faith from ‘truth’ to ‘one possible truth among several.’ The second position clashes fundamentally with the idea of equal human worth. It also clashes the the idea that god is benevolent: it hardly seems benevolent to damn children who are born into the wrong faith and, since most people simply adopt the faith of their parents, this situation applies to most people throughout history.