Prof,
Absolutely - religion has been a major, perhaps the major, source of conflict over the centuries. And it continues to be a key factor in many conflicts across the globe.
But if we become a little more local - I fail to see much 'uniting' rather than 'dividing' amongst adherents of the most widely followed religion in the UK, namely christianity. So in my local area, presuming it is fairly typical, perhaps 5% of local people might be active christians who attend worship. Are these people all united - not a bit of it. Within easy walking distance of my house I can think of at least eight separate christian denominations, each of which will consider their interpretation of dogma and practice to be correct and the other seven to be faulty in some respect. So much for unity.
And even amongst one denomination - CofE, there isn't much evidence of unity. There are nine CofE churches within about a 30 minute walk from me - I know plenty of people who are CofE worshippers. Do they go to the most conveniently located church? Not a bit of it, nope they attend the church that most closely aligns with their narrower interpretation still. So the evangelicals ignore perhaps three nearer churches to attend the most evangelical. The high-church cathedral types won't worship in more lowly churches, only the Abbey and so on.
And, of course each denominations wants its own schools to divide even further.
I still think the old Emo Philips joke put this best:
“Once I saw this guy on a bridge about to jump. I said, "Don't do it!" He said, "Nobody loves me." I said, "God loves you. Do you believe in God?"
He said, "Yes." I said, "Are you a Christian or a Jew?" He said, "A Christian." I said, "Me, too! Protestant or Catholic?" He said, "Protestant." I said, "Me, too! What franchise?" He said, "Baptist." I said, "Me, too! Northern Baptist or Southern Baptist?"
He said, "Northern Baptist." I said, "Me, too! Northern Conservative Baptist or Northern Liberal Baptist?"
He said, "Northern Conservative Baptist." I said, "Me, too!
Northern Conservative Baptist Great Lakes Region, or Northern Conservative Baptist Eastern Region?" He said, "Northern Conservative Baptist Great Lakes Region." I said, "Me, too!"
Northern Conservative†Baptist Great Lakes Region Council of 1879, or Northern Conservative Baptist Great Lakes Region Council of 1912?" He said, "Northern Conservative Baptist Great Lakes Region Council of 1912." I said, "Die, heretic!" And I pushed him over.”