IMO, the most admirable religious minds of today belong to those theologians who come to clearly understand one faith be it christianity, judaism, buddhism, whatever, and then go on to learn the teachings of others, discovering in which ways they are similar and in which ways they differ. While these men and women may live by the tenets of their chosen faith, they do not feel the need to denigrate those of other faiths, to cast them out as the "unchosen", nonbelievers doomed to some variety of eternal damnation. They see it as variations on a theme.
Conversely, those who view their religion as the "one true religion" have shut themselves off from the rest of the world. Us vs. Heathens. Fundamentalism is merely the highly condensed nucleus of this brand of elitism/isolationism.