Religion is what you make of it, imo. My cousin and her wife have been fully supported, included and treasured the way any other couple or person would be, as Liberals. And supporting same sex marriage and rights are formally supported by liberal and Reform Jews for example, in a way it isn't in other religions. But that's beside the point. Religion forms a rallying point around which many horrible people can oppress, kill, brainwash and discriminate against people. Religion is used to excuse and justify many, many horrible things. I see it as religion being a way people interpret the universe and their own feelings about life- and what life means - just like science does for the physical things, religion is a kind of emotional science as you work out why you think x is a good or bad thing, why you feel connected to this person or that idea.
People who are religious and do horrible things- eg, IS - would probably do horrible things if they were Christian, if they were Hindu, if they were atheist. I don't believe that ordinary, good people can be brainwashed enough as adults (different if they were raised in a family with those beliefs- but loads of stories have come pouring out, showing that many of the Britons fighting came from liberal, ordinary families, some of which weren't even Muslim) to do those things.
I think religion can be USED as a convenient way to hold power over people. It probably draws in a lot of power hungry people, you could say the same about Parliament. But that isn't, imo, a fault with religion itself, although it could well be to do with certain groups who practice- like saying 'BNP, National Front, UKIP, Respect' and saying political parties in the UK are wrong or violent or whatever. Religion provides comfort, hope and connection to people. It is entirely natural to have some sort of faith, not necessarily religious.