I thought I was an atheist till I went to an atheist service. Oddly the service was on a Sunday morning, and the songs sung were melodies of Christian hymns but with anti Christian verses. I'd never thought of "atheism" as being anti-Christ, but after that service I stopped calling myself an atheist and became an agnostic. I wonder this: how many others call themselves ___, but have been to a atheist service.
Seems to me it was an antitheist service you attended.
I guess ever atheist service is different, and I question what percentage of atheists want to go to any Sunday morning service. I attended a Unitarian Church where Jesus and God were never mentioned, but at another Unitarian Church every other Sunday was a Christian service. All faiths vary to some degree.