I do not think of the devil as a real being either, and I did point out that I do not think that people who go to church, as being godly, ie better or more rightious than the rest of us. I say this for the exact reasons you mentioned,BUT evil does exist, everybody knows that. Everybody knows that love exists also, but it does not mean they think God exists anymore than "the LOch Ness Monster"
The problems you say are caused by religion are not caused by religion itself, they are caused by human nature. People who follow religion are not exempt, which is again the point you were making. Religion and beliefs stir up very strong emmotions in people, but it is the imperfection of people that cause the problem.
YOu would not blame violense at a football match on the football would you. Again it is human nature that is the problem.