Unless you're arguing for the elimination of the market system, "this structure in a market economy is prone to corruption" isn't a dispositive argument, or really an argument at all.
If we aren't discouraging the first, why the second?
Similarly, ownership and capital has a tendency to view labor as a black-box machine. If the machine, when operated in Indonesia, produces comparable financial results, what's the point in running the machine in the US? And so pretty much ever job that can be outsourced is outsourced.
Management can have the worst of both worlds. Most managers are hired guns. A ten-year stint at the helm of a company is a respectable tenure, but it's a short period of time compared to the life of some firms. Management in large firms routinely harms both employees and the long-term prospects of the firm by optimizing for short-term metric gains that boost their own compensation.
There's no part of the system that works flawlessly, or isn't freighted with obvious problems. It's kind of a miracle that things work at all. Nevertheless, they often do. And they work better for everyone when all the stakeholders are organized and engaged.
There're always issues of misaligned or perverse incentives. Although I have no illusions about union leaders having a particular interest in company success, it's not worse than company management having no particular interest in company success. And, since they have less power, they have less of a negative impact on the company and society in general.
The problem is when the company is a monopoly, which should be carefully monitored.
Because his fact-free attack is demonstrably wrong. The majority of unions are invested in the companies they provide labor for. By way of example, Germany has unions that are evidently committed to the company's existence - to the extent that labor being represented at board level is not unusual. That is the kind of, ahem, synergy that should exist between capital and labor, but is anathema in the US.
In contrast, some executives are effectively mercenaries with no interest in the long-term survival of companies, they work on very short horizons, but I never hear anyone demanding that management is toxic and shouldn't exist.