But you still have to define income, don't you? And that definition has at its core the exact same situation you claim in untenable. Because any definition of income is inherently just another way of describing the deductions.
But now I understand your point of view - you are enamored with flat taxes and ignore the problem of defining taxable income.
The things we're talking about on this thread have nothing to do with defining personal income. For example, why should you deduct state and local taxes to calculate federal and not deduct federal before calculating state and local? All 3 of those entities have an income tax (and most of the country has 0 % local income tax). Food and housing are primary to state and local in terms of survival, yet they aren't deductible to feds. Healthcare and electricity and gasoline is primary to state and local in terms of survival, but they aren't deductible.
Now, if you have a primarily S corp filer, things can get more complicated for income, but the US tax code isn't primarily aimed at S-corp filers. It's aimed at W2 filers. You may not like that, but that is the vast majority of personal income in the US, with most of the rest being capital gains.
The fact of the matter is you personally benefit from the deductions in question which is why you want them. Pure selfishness. That's fine, but at least own up to it.