Im so pleased that you chose to make that point in the disarming form of a question. Your point is such a good and important one.
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 doesnt gain enough supporters to carry the day.
And the reality is that its 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. ;-)