The very moment we like/hate someone soley on the foundation that we've discovered their true theist/atheist beliefs, something is very wrong:
"Hello, is this God? NO! oh, it's the church... yes, close enough. I'd love for you to define my life completely for me, yes, here's my money too."
The Devil vs God? Good vs Evil... it's ying and yang. Which is ying and which is yang? I never could figure that out... And why is it that the classical saying "In the name of God" seems to kill more people than in the name of Satan? What's with that? When religous radicalists are yelling into mics, there never seems to be any mention of the Devil, ect, next to killing people and their kids. I guess God needs to do the killing and Satan takes credit? I dunno, maybe they did mention Satan and I had already tuned the sound of their voices out.
As doward pointed out, faith is a powerful thing that can do both alot of good and/or alot of bad. Some of the most cruel and demented tourcher techniques in written history were used in the name of God... as well plenty of genocides and slaughters. And also alot of charity and compassion.
It's easy to forget the good that religous groups have done when weighed against the bad. The obvious problem is that the good will never exist without the bad, something has to give. Missionary Orphanages and such, while very aimaible pursuits, could exist without the zealotry that burns them down if you remove the missionary and keep the orphanage.
How does the devil show himself in my daily life? He doesn't... I play poker with him the first tuesday of every month. Allah, Moses, Jesus, Odin, the Flying Spaghetti Monster, and even Zues are there to, and every odd month Jupiter shows up and takes everyone's money. That bastard can really bluff I tell you what...