I think the argument that he is making is that work visas are used to increase the labor pool (creating a "buyers market" for companies that are hiring). If a company cant find anyone willing to accept their offer then they need to improve the compensation and working environment... or they could hire a worker from the visa pool, thus suppressing wages, benefits, WLB, etc...
It's labor-economics 101.
It doesn't matter what the job is, if you pay enough then someone will take the job (and become qualified if needed).
ex: I'd scrub the shit out of sewage pipes with a toothbrush if you paid me enough, but most companies would just say that there is a "skilled labor shortage".