@Arella Mae,
In view of that Arella you would help the cause of Christianity by staying away from discussions on the matter and leave the defence of it to those who do know why they support it. The position "I just do" is as equally vulnerable to attack as, say, a belief in flying saucers or any of the 30,000 pagan gods and goddesses. And the position allows the atheists a free rein to influence people many of whom are only too ready to set aside Christian teachings.
Christianity should be defended pragmatically. On its utility. Which allows the argument to enter the debate concerning the utility of atheism. I agree that atheists, when challenged on that point, will select Ignore, as it stumps them, but that is all to the good as people will see it and draw the only conclusion possible: that they have no answer to it and therefore they are attempting to lead people into the dark.
Only a fool would follow somebody who doesn't know the destination his opinions lead to. The destination Christianity has led to can be seen through the window. Abolishing Christianity and embracing atheism is not an abstract concept. It is an entirely pragmatic position. Either for the individual who seeks freedom from Christian sexual inhibitions or for a political policy which views Christianity as less useful for the future social organisation than atheistic materialism. Both of which positions can be, and have been, defended in ways that are not really refutable except by lengthy philosophical arguments which are never conclusive.
What you should focus on is the question of what an atheist government, which your opponents have to be aiming for to have any credibility, will replace Christion inhibition of sexual licence with or admit that those inhibitions are no longer of any use. And inhibitions of biological research. Or inhibitions of free speech.
They would, for example, be obliged to agree an age of consent on scientific principles. The evolutionists, as they all are, supporting a considerable lowering of it on biological grounds read off nature. And a national DNA database established in order to find out who is who's father and mother and grandfather and grandmother. Which is an interesting question.
Watch them creep away when you get them in a corner on such substantive arguments. What do we get if they convert us all and it is very tempting to be converted to atheism. But the Devil only has the best tunes for the first few bars. A bit like cocaine.