The hate starts with our fundamental sense of fairness. Studies with monkeys demonstrate that a desire for fairness is a fundamental element for any highly social, co-operative species.
When I was a child, I was told that God was real and we had to go to church every Sunday. When the plate of money came around, I thought it was God paying us for our worship and praise; when I found out I had to put money into that plate, I didn't think it was fair that a God that created everything would need my money. I focused my attention to where it belonged, but that wasn't always the case.
Before I got to join the congregation upstairs, I had to spend many Sundays in the basement of the church in Sunday School with some other kids. Every Sunday, I had to get up early, dress up in tacky clothes, and go to Sunday School to learn about God. This meant that I couldn't stay up late Saturday night. The only night I could stay up late was Friday night, but I was usually pretty tired by the end of Friday, because I had to get up early for school Friday morning, which meant that I didn't get to stay up late on any night of the week. When I went to school the following Monday, the kids were talking about how funny Saturday Night Live was. I hated them for getting to skip out on church Sunday morning and enjoying that bit of comedy, and then sharing the experience.
When I learned that there were kids who didn't have to go to church on Sunday, who got to sleep in after staying up late Saturday night and who got to ride dirt bikes or lounged by the pool on Sunday, dirt bikes and swimming pools we couldn't afford because in part the church took 10% of the family income, it wasn't fair. The only way I could square that in my mind was to hate the non-religious heathens, and the only way I could cope with that hatred was to believe I was somehow better than them. God was real and He loved me and I was going to go to heaven, a place they wouldn't get to go to. Fortunately for me, my mind couldn't work that way for very long, as it was always wondering. There were kids who knew that Santa Claus wasn't real, and they still got great gifts for Christmas, maybe they had some knowledge that I didn't have? When I considered this, the thought of them not sharing this knowledge really made me hate them.
This is why I believe atheism is important, because atheism is the least hateful position to be in. By calling myself an atheist, I'm being open and honest with people who still believe. I'm not holding anything back from them about how I've made my life so great. I can understand why someone who earns his or her living from the collection plate would want to preach hatred of atheists, because once people realize how much better life is without religion, they've just lost a source of labour-free income. I can understand how those putting their money in the collection plate for a very long time would want to agree with this sentiment; the thought of missed opportunities must be unbearable, just like the thought of leaving a slot machine that will pay out sometime must be unbearable to the adult diaper-wearing gambler. http://www.aproundtable.org/news/newsindividual.cfm?ID=1798&issuecode=casino
Religion not only creates hate, it is the cause of many of the problems of society because of this hate. Any good the mainstream religions may do is mitigated by the inherent hate they create in their congregation by generating a demonstrably false world view in its congregation. If religions truly wanted to make the world a better place, they would refund the tithes that were given to them and re-establish themselves as charities that serve a cause, such as world hunger, climate change, and clean drinking water for everyone, and then ask for that 10%.
Of course, this will never happen, because actually fixing the problems of the world requires real actual work, and those who rise to the pulpit tend to shun doing any real work, preferring to cherry-pick the bible and telling people what they want to hear, rather than what they need to hear.