The argument being made is that employers have a lot more market power in the employment market than potential employees. Employers have capital, they have inertia so they can absorb a lot more risk. There are fewer employers than employees so it is easy for them to form a cartel or engage in price fixing. This especially goes for low end jobs, where a small number of large corporations make up much of the retail and fast food market. Unemployed individuals are under a lot of pressure to find employment quickly, and they know there is a lot of competition. So, employers can set wages artificially low. This power is not absolute, which explains why not every job is at minimum wage. However, this is an observable effect. The gap between rich and poor is ever widening, the middle class is eroding away, yet all the while production has been increasing. Wages are being driven down artificially low.
I wanted to ask "where does it all end?" but then I realised from the rest of your comment, you actually seem okay with slavery. Which is odd really, because you argue about human rights, but the right to freedom of movement is actually a far more fundamental and clear cut human right than the right to form contracts and do trade. In fact, if your ideals about the right to form contracts result in other people losing their right to freedom of movement, then that's a clear sign that you have lost your way.
The "gap" between the rich and poor is a function of possible productivity. As it becomes possible for people to do more, there will be more of a spread between people who do nothing and people who max out their potential. When all farmers worked farmed by hand, the "gap" between the lazy and the industrious was a few bushels of food. But now that there are tractors and financing available, the top farmers produce maybe thousands of times more than the little farmers.
The situation is similar in every field, especially those involving mass distributions. An interesting youtube video can get millions of times more views than an ordinary video. Is this a problem? Should we force people to watch uninteresting videos, or cap the interesting videos to reduce the viewing gap?
I don't see why increased productivity should be a concern, especially since being productive today generally means imparting benefits to large numbers of people. Larry Page is very rich, but he got that way by helping everybody with an internet connection to find useful information.
> . . . the middle class is eroding away, yet all the while production has been increasing. Wages are being driven down artificially low.
I don't understand what you mean by "artificially low" wages. Wages are generally set by supply and demand. As long as people are free to choose alternatives, they are not working for artificially low wages. An example of people with artificially low wages are prisoners who must take the work offered to them by prison officials. But the majority of people are not in prison.
> you actually seem okay with slavery
I'm all for stamping out slavery where it is committed by one person against another. No one should take away another's right to contract. But where a person voluntarily degrades himself, I see that as his choice, not mine.
> the right to freedom of movement is actually a far more fundamental and clear cut human right than the right to form contracts and do trade.
I agree that freedom of movement is a fundamental right. I'm not sure if it's more important that the right to contract or trade. I think it's less fundamental because there are a few situations where you could legitimately not have freedom of movement (while traveling in an airplane or trespassing), but I can think of very few situations where you wouldn't have the right to contract. (You might have contracted away your right to make future contracts for a limited time and subject-matter.)
I wanted to ask "where does it all end?" but then I realised from the rest of your comment, you actually seem okay with slavery. Which is odd really, because you argue about human rights, but the right to freedom of movement is actually a far more fundamental and clear cut human right than the right to form contracts and do trade. In fact, if your ideals about the right to form contracts result in other people losing their right to freedom of movement, then that's a clear sign that you have lost your way.