> If anything, taxing corporations is regressive
No, its not.
> the taxes ultimately get passed on to consumers through higher product prices, regardless of their income levels.
It increases producer prices which shifts the supply curve to the right, but its pretty self-evident that the effect on actual prices is dependent on price elasticity of demand in the markets for particular products, and that price elasticity of demand is not independent of the income of the people in the market for the product.
> Taxing corporations doesn't produce magic money -- it's still taxing people in the end, but it's the consumers.
No more than taxing labor income (which the US does disproportionately, as much capital income faces lower income tax rates and labor income is subject to additional, non-income taxes) is really taxing corporate stockholders, because it shifts the supply curve for labor increasing market clearing prices of labor and eating into corporate profit margins.
> We should be taxing the people who own the corporations, or are paid huge salaries by them -- that is, if you believe in progressive taxation.
But taxing high salaries is "regressive", just as much as taxing corporations, taxing consumers -- after all, if you shift the supply curve for management work and increase the market clearing price of that good, you are increasing producer costs and, therefore, shifting the supply curve for the good produced in a way which increases the market clearing cost, resulting in price increases to the consumer to pay the taxes. If you are going to make this argument for corporate taxes, you have to apply it to whatever you present as the alternative to corporate taxes, as well.