You know, that's something I've always asked, and when I was at bible college I asked that very question and the lecturer could never find the answer to that one...
It seems so simple to me, as the church is the church right? One unified group serving the same purpose... but it's not so simple... the pastor I worked for when I was an intern (we're going back a wee while now) said to me that there are different flavours of God and that some flavours just plainly don't mix... I'm guessing because he didn't particularly like some of the other churches in the area and refused to work with them (they were really neat people I did a bit of community work with them and I'm still friends with them to this day)... goodness knows what he was so hung up about...
We all have differing opinions, but there are three parts to what makes up our spiritual identity in the christian church there is Dogma (the really important stuff, like knowing and believing that Jesus died on the cross and that he rose again,the triune God as in Father, Spirit, Son etc the bare essential teachings), there is Doctrine (whether or not church is on a saturday or sunday, or whether or not somebody is a member of the church when they are christened as a child or fully emersed baptised as an adult) and then there is Opinion (prayers should be freeform and shared in the form of prayer books, only King James bibles shold be used to write a sermon on and all christians should dress fancy when they go to church etc)
You see it's very easy to get so hung up about our opinions because we're all so unique, our opinions become almost like our prejudices (and I'm not talking rascism or sexism etc) I'm talking about our automatic view of how things should be (whether that be a positive thing or a negative thing), so we enforce it on others. Truth be said it's such a human thing to do... we argue and bicker until the cows come home!
That's how I'd explain it...
The bible does say something about 'judging a tree by the fruit that it bares' (or something along those lines) in other words, if something doesn't feel quite right or if you think something is wrong, check it out in the bible and measure how accurate it is...
I hope that answers your question...
Aroha Nui (much love)
*E-J*