I've always believed that religion has two main pilars that brought it into the world, and it still rests on.
First of all, the need of people to be able to explain everything they see. Anything they can't explain must be devine, because what else is there? Some things that were devine in the past (lightning, sunrise spring to mind) are not anymore now. But there will always be things that are inexplainable. You can argue over the origin of the universe, and if you can conclusively show that it wasn't a devine being there will be other things, up until "what's after death" and you'll be stuck nonetheless. There's hardly a reason to debate about this really, it's up to what people believe (usually, that's what they were brought up with...).
The second pilar is the really annoying one, the need for people to want to belong to a group. It creates the feeling of "us" (funnily shown by Toddy top page 2, btw), the need to care for others within your group (and sometimes even outside your group) in many ways which is great.
But it also creates the feeling of "them". The other side, the rest, the ones that don't believe what we do. They think different, and since what we believe is right, they must be wrong. For some reason, many people need a common enemy to make the bonds within their own group tighter.
You can debate that religion is one of the basis that extremist groups are build on, but if religion isn't around people will find other beliefs to get the exact same. Multitude of examples; left-wing, right-wing, green-wing, hooligans, gangs...
Ín my mind therefore, there's not much use debating religion.
I'm a believer in Star Trek's theory: As soon as people will find out they are not alone in the universe, they'll realise the differences between them all are minor and we'll have a new common "enemy". It's only when we realise we are all alike, and are one group of people when peace will become an option (come back in a couple of thousand years, i think...).