"...many companies find ways to skirt corporate tax... but not all, and not really the majority (but preferentially the huge companies)"
So that's basically the case for progressive corporate tax. Everyone acknowledges that small/medium business pay the full tax rate, while large/huge corps always never anything close to it. With progressive taxation you can directly impact the latter and not the former.
Why tax productivity at all? A land value tax redistributes gains in productivity to the government in the form of tax levied on the value of land - the value of the improvements on the land.
So that's basically the case for progressive corporate tax. Everyone acknowledges that small/medium business pay the full tax rate, while large/huge corps always never anything close to it. With progressive taxation you can directly impact the latter and not the former.