I guess he's given up on this silly assertion.It's not silly, it's basic microeconomics (really basic). Go pick up a text book (and read it).
Although I've been through the econ courses as many of us have, the real world is the true text. Words on pages make for interesting thoeries, but not so accurate sometimes.
My price would be way less if not for the taxes (income taxes included) I pay. There is absolutely no refuting that. Maybe I misunderstand your assertion - it is absurd as I understand it - that income tax is not paid from my sales revenues and does not affect my price.