Oh, yes, that's all familiar and makes sense, and I accept that taxing corporate profits isn't necessarily an effective way of taxing capital income (although I think the problem of finding a system of taxation which makes it clear where the burden falls, can't be easily avoided, and is efficient to collect is a hard problem, and becomes harder when you add the constraints of wanting a certain level of progressiveness* and wanting to minimise disincentives to production).

I was specifically querying the final line of the first paragraph - "Similarly, given that we are all economically literate, we know that capital income should be taxed rather more lightly than labour income, if it should be taxed at all." - which is a more general assertion, and not one that I've seen made before.

*Our assessment of the optimal level here may differ, but I'm sure we can agree that there is an optimum