Have you ever found a religious person that was genuinely interested in hearing what you had to say from an atheist perspective? I've found that if you tell people that you're an agnostic, they may engage you in conversation in an effort to illustrate to you that their god is real, but if you're an atheist, they're more likely to berate you or simply refuse to listen to your opinion.
I remember a conversation I has last year with one of the nicest people on earth, she happens to be very religious, perhaps due to the loss of her son some years ago. Anyway, we got to talking one day about churches here on the island, and I had to tell her that I'm atheist. She was visibly taken aback, and then admitted that she's so sheltered she doesn't think she's ever met an atheist. I know she's always thought of me as a nice person with good values, and that didn't change. In fact, she left a flower on my doorstep after that conversation. She's still one of the nicest people on earth. We didn't argue our difference in beliefs - it simply didn't matter.
I have found that in the last few years many churches, especially charasmatic ones, have put forward the atheist (not satan worshippers as in the past) as the real enemy of god. I see reports daily about churches blaming atheist, gays or abortion for any trouble under the sun. I am an atheist and would not tell anyone I'm agnostic as that would be immoral. I do believe that most believers don't know what an agnostic believes and would be more willing to engage with you.
I have found the following reactions:
I think it's import that people know when you are not religious or atheist. Probably for the same reason religious people want you to know. If you want to know about christinity then you will find a openly christian person to talk to. It's the same with being an atheist. If people know you and see you are a good person but yet you are an atheist they will ask you about it and then you can tell them what they need to hear. You will never get someone away from religion unless they are ready to go.
As an atheist I do sell logic, reason and freedom from religion. This makes the religious correct in calling us their enemy...
Haven't met the christian yet who listened to my point of view whether I identify as an agnostic or atheist.
There is a little variation within the Christian faith. The more fundamental become very angry at athiesm. My experience with the bible bashing door knocker has been varied. Mormons tend to view me as an iconoclastic anti-Christ but the Jehovas Witnesses tseem to take pity. Incidently I've noticed a pleasant change in the Jehovas. At the last encounter they didn't try to shove a Watch Tower on me a beat a hasty retreat. They had literature on community welfare and we had a pleasant discussion around those issues.