I think, they are arguing from a deregulated/free market capitalist perspective. Supposedly workers can freely chose to whom they sell their working capacity a

I think, they are arguing from a deregulated/free market capitalist perspective. Supposedly workers can freely chose to whom they sell their working capacity and thus can negotiate a fair share of the value created. I personally don't see that working, at least not with strong union laws or even complete syndicalisation of all means of production; the global worker pool and the mobility of companies (vs. the immobility of workers) gives companies just too much of an edge in this negotiation (at least outside of bourgeoisie knowledge workers). As evidence I point to the decoupling of company earnings vs. labor income share since the 1980ies.