Your rather extreme libertarian views have really well thought out rebuttals and it makes me think you haven't actually read much to challenge these ideas of yours. I have major libertarian tendencies and I find your arguments extremely wanting. This is like level 1 libertarianism, where all the arguments, if taken to their natural conclusion, result in a tax rate of 0%.
Aside from the larger question of why the government has the right to take people's income by force to begin with
Because the government provides services that you cannot "opt-out" of. You benefit from services (ie, defense), no matter how much you try not to, by merely living within the borders. This is our "social contract". The free-rider problem makes this an essentially necessary part of any modern society.
It is a disincentive to others who might try to reach that level
And your argument ignores the incentives to reach that level (ie, being rich). They are two forces that MUST be balanced. Ignoring the incentives, I can see how you'd view all taxes as ONLY disincentive. This ignores the reality of the situation, however.
It's hardly clear that the success of the wealthy is due to how society is structured, and not their own effort. Undoubtably some is, but is it 90/10 or 10/90?
It's actually quite clear on issues that take very much for granted. Like binding contract law, law and order, due process, and so on. Even still, no matter what the split, the rich -do- benefit from these more than the poor. This is a rather poor argument, though, because even if the rich didn't benefit more than the poor, the progressive tax system is moral for other reasons (decreasing marginal utility of a dollar, most importantly).
It encourages relocation of talent, business, and capital to states or countries where the tax situation is more favorable.
Yes, an economic factor that MUST be considered. Again, pretending that all tax raises are bad for a reason like this implies that the optimal tax rate is 0%.
It's not clear to me that more tax revenue results in a net benefit to society. My opinion is that the rich are better at investing their money for optimum yield than the government, and the end result is more benefit for society.
Is -any- tax revenue a net benefit to society? Or is the optimum zero? If you believe that the optimum is above zero, then you MUST acknowledge that taxes can be too low, and must raised.
Any (libertarian) argument that tends to natural conclusion in an optimal tax rate of zero can be discarded as poorly thought-out. On the flip-side, any (socialist) argument that tends to the natural conclusion of an optimal tax rate of 100% can be equally discarded.