The law of supply and demand is not a physical (Law of Gravity) or mathematical (Law of Sines) law because there is no economic universe per se. Economic concepts are solely the consequence of social relations, they deal with human activities and only make sense in terms of transactions between people. If the worker is getting screwed, its not because of some abstract law of nature, its because his boss is screwing him. And yes, sometimes the tables are reversed and the worker screws the boss. But this is usually not the case because the boss generally has greater resources at his disposal. There is no law of supply and demand where there are no markets, or no customers and suppliers, or no people. Supply and demand affects prices, and there are no prices in nature, they only exist in social relations. You don't have prices unless you have buyers and sellers (or bosses and workers) and their prices are decided by negotiation, not by natural law.

Of course, bosses (or workers who want to be bosses when they grow up) can't be expected to see this. They have too much invested in the continuation of a system that benefits them to see it in any way that doesn't justify their own desires and expectations. They need to have an excuse to screw people, or to make themselves feel better when they are being screwed. The genius of American business is that it has been able to convince its workers (and customers) to allow themselves to be repeatedly screwed because ONE DAY, if they work hard, follow the rules, and don't cause trouble, they can be bosses too and screw their own workers.

Its the same lie the plantation owners fed Johnny Reb. Don't fall for it.