You may find it confusing but it's not really a problem and you're not alone in mixing your interests.
One of the most talented contributors we ever had on Ask was a guy named Melloblue. Lawyer, teacher, artist, musician, marine sergeant, and atheist. He also sings with a Christian choir which travels internationally giving recitals. He said they all know that he's an atheist but they call him their "evil influence".
No, not at all. I mean sometimes you have to have other perspectives in order to see anything. I don't know what you mean by group, though. You mean something like a church? If you're atheist, then don't worry about it. You don't have to change for other people.
I still go to Church with my wife, who is a believer.
Here's a game you can try: Every time the worship song or the sermon says "God" or "Jesus" or "Heavenly Father" just replace that in your mind with FSM. "Fizzzuuumm" works really well in songs about "Jeeeeesuuuuuss".
And nothing about the message changes. It's amazing how much FSM loves us!!
It is not bad. It is your choice. True Christian groups allow anybody to attend. But it does not matter what they or others think. It is what you think. You have your own beliefs. If you are comfortable with your choice to be there and comfortable with the way you are treated by them then how can it be bad.
Of course it's not bad. From the Christian perspective they are there to spread the message to the nonbeliever, as well as to fellowship together as believers. - I am curious about one thing. Do you tell them your an atheist? If yes, what's their reaction? If not, are you intentionally trying to be deceptive for some reason?
my humble thoughts on the subject: knowledge is power. if you choose to believe or not is an individual choice. at some point, you will be asked how and why you made your choice. it is helpful to know the answer. secondly, knowledge helps people to understand an opinion different from their own, increasing tolerance. if more people would practice using their knowledge and tolerance, can you imagine the respect that we could show to each other?