When we debate believers, what is the goal?
Proving to the other side that god doesn't exist? Proving that creationism is silly? Proving that morals are independent of religion? Proving that religion is bad for humanity?
What about proselytizing? Is that what atheists are doing as well? Trying to sell non-belief to believers?
I have a problem with doing this. Meaning, while it's fine to debate believers, I don't think we should be trying to convert believers. At least not by proving that god doesn't exist or that religion is bad. I think those are negative approaches.
I certainly didn't become an atheist because someone convinced me otherwise. I did it because I convinced myself. I sought after the truth by seeking knowledge of the world around me. I learned about the tenacity of life and its seeming impossibility within our universe. I learned some basics in many fields of science before I let go of my belief. Personally, I think it is the only real way to do it. Otherwise you leave those who were believers standing on less than solid ground. They want certainty but they've lost it because they don't have the knowledge to reinforce their mind.
I'm not saying that you shouldn't try to convince believers, I'm just saying that if you're going to do so, do it positively by teaching some basics about the universe we all live in. Provide the person with a place they can go to learn more about the various fields of science. Be aware that you should be pulling the rug out from under someone that may not know enough to keep standing. Lastly, there is also the possibility that one of these people might fall into the fallacy of thinking that since there is go deity, there are no rules and therefore anything is possible, including murder, rape, stealing, and whatever else. For some people it really is the thought of an all-powerful, all-knowing, all-seeing deity watching over their shoulders which keeps them in check.