Unjust level of taxation?

Jim Henley asks what level of taxation liberals would consider unjust, as opposed to inefficient or unwise. Yglesias offers an answer, as does Kevin Drum.

But I have a different take on this question. According to Anglo-American liberal thought, from Locke down to the Framers, the question regarding the legitimacy of taxation is not the level of the taxation but rather the procedure by which that rate is set. Thus, "no taxation without representation." My answer is thus that there is, a priori, no unjust tax rate, not even a "confiscatory" 100% top-marginal rate. The question is whether the proper procedures were followed in imposing the tax, not the level of the tax itself.

Now, I can think of some exceptions here, but the general point is a valid one. If the legislature is representative of the people, and it passes a tax increase by the proper procedures, then that tax increase is, at least, presumptively "just," regardless of the rate. It is impossible, before the fact, to say what level of taxation will be necessary to achieve the governmental purposes set by the legislature; thus, we cannot say, before the fact, what is just and what is not.

It's possible to argue that the legislature is not properly representative, which is a whole other question.