Arguments framed in terms of morality are great for persuading others who share our moral views and who are therefore more or less predisposed to agree with us anyway. Much of the time, though, “preaching to the choir” just doesn’t gain enough supporters to carry the day.
And the reality is that it’s next to impossible, by repetitive recitation of our moral views alone, to persuade those people who do not themselves share those views. Attempting to pummel people or trying to shame them into “agreement” is usually a complete (and very ugly) waste of time and energy. Like you say, it becomes necessary at that point to find some other common ground (like logic and reason) upon which an appeal to those particular people can be based.
Another great column, Cathryn. Keep up the good work. ;-)
Whether it persuades the atheist philistines is wholly unimportant. Of course it won't persuade them. You don't put up a fence to "persuade" a wild dog not to trspass on your property. You do it to mark the territory in a way that even a dog can understand.