Maybe I'm missing something, because almost all arguments to the effect that people have no moral right to their pretax income (such that taxation would require a special moral justification) and therefore taxation is legit, are plain non-sequiturs.
For instance, Ronald Dworkin argues in Is Democracy Possible Here that the status quo system of political and economic institutions is the result of what he calls “the political settlement.” Because the distribution of incomes is to a large extent a function of these institutions, it is to that extent a function of the political settlement. But the political settlement is either morally justified or it is unjustified. At this point the argument goes something like this (and please correct me if this is too vulgar or innacurate a sketch):
(1) If you have a moral claim to your pretax income, then the political settlement is justified.
(2) The political settlement is not justified.
So (3) You have no moral claim to your pretax income.
(4) If the political settlement is morally justified, then it implements X scheme of income redistribution.
(5) If a justified political settlement implements X scheme of income distribution, then there is no moral right to pretax income.
So (6) No justified political settlement is one in which there is a moral right to pretax income.
Suppose you think this is a drop-dead valid argument. What does it NOT imply?
(7) The government, under the status quo political settlement, may legitimately confiscate pretax income.
Because, of course, the legitimacy of state coercion also depends on the moral justification of the political settlement. For example, if runaway economic inequality has led to political inequality, which has led to takeover of the state by oligarchic elites resulting in a mere shell of genuine democracy, then obviously that government lacks a mandate to use force legitimately.
If (1) Is true, then so is
(8) If the exercise of state coercion is legitimate, then the political settlement is morally justified.
(7) really doesn't follow because Dworkin explicity argues that a certain scheme of redistribution is a necessary condition for the legitimacy of government, and that we are now falling short of it! So then the government is not legitimate, right? And that's just to say that it is not justified in its use of coercion. So Dworkin seems offer an argument to the effect that (a) You don't have a moral claim to your pretax income and (b) it would be wrong for the government to collect taxes. An illegitimate government has no moral claim to your income either, no matter how illegimate your claim! But Dworkin thinks his is an argument to the effect that it is morally mandatory that the status quo government take more in taxes. Puzzling.
Dworkin does allow for degrees of legitimacy. But it seems like he's still stuck with the problem that if things get too bad, according to his lights, then it's wrong for the government to do anything about it. And if the government has a pretty secure mandate to legitimately act, things can't be all that bad, and peoples' moral claims to what they're now left with post-tax must be more or less secure.
What am I missing?
For me, the general lesson is that political philosophy is rife with unprincipled violations of analytical symmetry. If luck vitiates rights to incomes, then it also vitiates rights to hold and exercise political power. If there are common preconditions for the legitimacy of property rights and the legitimacy of political power, then the failure of those preconditions cannot be part of an argument for the legitimate government expropriation of illegitimate property. Etc.