[nietzreznor]

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Really?? Meaning the last point? Suppose in some weird sense it could be shown to be moral to hold your own head under water till you suffered brain damage, such that you could never again voluntarily hold your own head underwater. (Yes, it's a weird example.) Would you not think the fact that it was self-defeating would almost have to undermine the argument (of whatever nature) that it was moral to do the act in the first place?

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It is hard to even comment on this sense the example is so weird and so completely out of context (one might be inclined to do something of the sort, say, if holding your head under water would somehow save your child). But, yes, in most circumstances, if doing something was really self-defeating then one wouldn't have a moral obligation to do it.

In any case, I don't hold the position that consequences and questions about 'whether things work' is unimportant--I just don't think it's the only important question. Certainly we should tend to do things that work, but just as certainly not in the case when the means are bad in and of themselves. Thus, even if we found a tax that worked really well (be it for some small group of people, or some magic tax that was somehow pareto optimal), I would still oppose it because the ends don't justify the means.