Very nicely put Joe! I like this - clear, concise, rational and to the point. I suspect that Catholics may take issue with the idea that we were all born atheists -they would probably argue that if your parents are catholic then you are born catholic, an idea that I find disturbing.
I also like Richard Dawkins idea that even religious people are atheistic since they reject the other 3,000+ gods that humans have worshiped through history. Atheists have just gone one god further!
I want to tell them, "I don't agree that atheists are immoral or insensitive. And many believers are insensitive".
The contexts, the questioners' styles, vary.
The mildest was the man who helps anyone he can but, from in the two years I've known him has not once shown me he is capable of a complex thought. In as calm a manner as I've ever heard, he told me I would come around some day. I ignored him that time but we are both members of a writers group and a Toastmasters club so we communicate on other issues. The harshest was the man who last year, with as much certainty as I've ever heard from anyone on any subject, told me that after I die I will be on my knees to Jesus. I learned from his wife that before a recent stroke he hadn't talked like that. He and I nod when we see each other.
To those on the polite end of this range, when a response is necessary I say either "If my dad hadn't sent me to Catholic schools I might still believe a god exists" or "I'm a born again agnostic; I knew nothing of gods until I heard of one in the Catholic school my dad sent me to. In college I returned to agnosticism, but having seen no evidence since then I climbed down off the fence on the atheist side."
To those on the harsh end of the above range, when a response is necessary I say "Religion is the biggest fraud that has ever been perpetrated on humankind." It has shock value.
While in college a few Catholics told me I shouldn't throw the baby out with the bathwater. For a while I had no reply. Then I realized that the baby, Catholicism, had so polluted the bathwater that I had to throw them both out.
About 15 years ago, when a woman announced with conviction that I was on a fence, I took several minutes to tell her how much skill being on a fence, and not falling off, requires. She soon looked so confused that I almost felt sorry for her.