This is the other side of free trade that progressives are loathe to talk about for some reason that is beyond me.

It seems to me that "big business" and corporations are perceived as the enemy, keeping the people down, and it would be heretical to admit that corporations are in fact composed of people, and that corporations prosper by helping people prosper (employees, investors, partners and customers).

In the video of this post, Dr. Harvey makes a simplistic statement that business always wants to lower wages because it means more profit. Business must want to raise prices too, what stops them? What if business increases payroll, increases production, and increases revenue? That means more profit too, doesn't it? Don't successful companies grow, providing more and more people with jobs? Aren't many of those jobs middle management and above, at least, with higher salaries?

China hasn't really pulled 680m people out of poverty since '81; the US and EU have via offshoring manufacturing to the East.

If we want to give credit where it is due, the U.S. and E.U. aren't responsible either. They just had to get out of the way. It's big business again, especially multinationals like Apple, Wal-Mart, and (gulp) Amazon which enabled people with money who wanted things to strike deals with people with manufacturing skills who wanted money. That's putting it a bit simply, but it seems more fair than giving credit to governments which, at most, reduced the obstructions to trade that they had created.

the share of national income that goes to labor and to capital. We know that there must exist an optimum

I would like to know how you even distinguish labor and capital. Everyone who works at a corporation performs labor. Investors may not, but most of them work elsewhere, and many of them are "little people" who invest via 401(k) accounts, depositing funds in banks, or playing in the stock market.

You acknowledge that free trade has been remarkably effective at generating the wealth which directly reduces extreme poverty, and does so at a rate "beyond anyone's wildest dreams." Why mess with it? Why assume that you or anyone else can make it work even better by interfering?