I did phrase my rebuttal as a question, but that re-rebuttal sounds like just another dodge in the spirit of "capital gains taxes are double taxation even though we fought tooth and nail to have corporations treated as distinct persons, separating their income from that of shareholders."

I am aware of the distinction, but, IMHO, you make far too much of it. You argued federal taxes must be considered in conjunction with state and local taxes (and, as I said at the time, I strongly agree; it is an issue often ignored in vitriolic complaints against oppressive federal taxes.) I responded that "to the extent the latter are deducted from the former they are included in, not an addition to, federal income tax." Deductions lowering the amount of income federally taxed rather than directly lowering the tax itself does not significantly alter that. Income above a certain amount x is taxed; if income-x-state income tax>0, federal income tax is rightly owed. However, the federal tax includes the state tax by not taxing it.

In terms of the point you raised at the time (whether US corporate income tax is competive with other nations when local income income tax is added:) First and foremost, corporate income tax within political subdivisions is not unique to the US; Canada and Germany (to name just the ones I know of) have them also. If we want to trade simplicity for precision by considering local taxation, we must do so across the board. That will diminish the effects of corporations paying 18, 12 or 0% tax (instead of 38%) on billions in profits, but it will be no less egregious in terms of federal corporate income tax.

Even the overall effect will not be diminished much though, because corporate income tax is <10% in all but one place (the top earners in IA,) <9% in all but six others and <8% in all but ten others. Four states have no corporate income tax at all (not counting TX, which taxes either income or capital, whichever is higher, as a franchise tax.) Even in the case of the most profitable IA corporations, 12%+0% (or 12%, or even 18%) is not too bad for a corporation earning billions in profits, and quite competitive with any country where any corporation wants to maintain its headquarters. US companies build FACTORIES in Third World despotisms; they do NOT incorporate there, because the kind of governments willing to grant low corporate income tax rates tend to be the kind who simply seize corporate income if it becomes large enough to warrant the effort. For all the talk about Americas "extreme" corporate income tax costing us business, how many companies have actually left the US instead of simply moving their production?

As to the ad hominems... well, they are not the best way to bolster disingenuous arguments.