Declining Debate

I have noticed that when debating atheists, after a little back-and-forth, they bow out, unwilling to further justify their beliefs.

There are a couple plausible explanation for this practice:

 a) Perhaps I am really too annoying to carry on a dialogue with. Perhaps I fail to address or take seriously the arguments of my adversaries. Although I strongly disagree with this explanation, I understand that my bias for my own capabilities may be blinding me from my own flaws; thus, I mention this as a possible explanation.

b) Atheists' have an inner sense that their position is actually untenable. Through debate, they become, consciously or subconsciously, aware of the fact that their initial confidence cannot be justified. This irks them and pains, and this pain compels them to stop debating.

c) Atheists are supremely confident that their position is right. When debating a religious person, they have the attitude that they are debating a foaming-at-the-mouth nutcase who really isn't worth their time, patience and efforts.

I suspect that "option c" is the most plausible reason for their reluctance to continue debating. And I believe that it is a lamentable explanation. Indeed, if nothing else, atheists owe it to their ancestors to continue subjecting their beliefs to scrutiny and debate. Never, ever be overconfident about your beliefs. Humans are extremely fallible and history tells us that each generation believes that it is "reasonable" and "rational" when compared to the the earlier ones. We should avoid such confidence and we should continue debating and subjecting our beliefs to debate. That is the only way to come closer to the truth.