Bullshit. Protectionism is getting everyone in America to pay more for the things they buy in order to subsidize a tiny group of people producing those things. Capital versus labor doesn’t enter into it, it’s just a way to hammer consumers to help the capitalists who own non-competitive domestic businesses.
If there is a balance of power between labor and capital, it is more likely true competition, a reasonable profit, and wages high enough to buy the goods produced will be the result. Remember Henry Ford? He paid his workers enough so they could affor a Ford.
Contrast that to CEOs who import H1b workers or send work overseas to increase the bottom line.