[Turn Prophet]

Well, Kant didn't have a large theory of Political Economy, so it's hard to say.

The Categorical Imperative has a tendency to be used to justify whatever people think is moral based off a separate moral system, so I'm not sure how far analogy will get us.

Kant basically thinks that you should act as though by acting, you were writing the universal moral law. Therefore, you should act as you want others to act. However, Kant also qualifies this by saying that moral actions are done out of a sense of duty for an absolute moral law, not out of self-interest. He also says that all actions must be taken, as the OP said, so that people are treated as ends in themselves, not simply as means.

So, if you think something akin to philosophical egoism is the universal moral law, and if you are right, Kant would have to agree that if you could deduce AC from your moral philosophy, then it would be moral.

However, I think Kant and a lot of other people take a pretty big exception to the proposition, "all taxes are theft." Also, it's often unclear in large-scale political decisions whether people are being treated as ends, not simply means. There is some room for argument there.

Really, so far as moral systems go, AC tends to be defended on the basis of either utilitarianism or some version of Political Economy (if you want the "for dummies" version, read Ayn Rand).