Actually it was not Capitalism that caused slavery. Slavery has existed forever. Certainly much longer than Capitalism. The worst slavery in the last several hundred year took place in totalitarian countries. By far the worst were Hitler’s Germany and most of the Communist states. A capitalist slave owner at least has some ownership interest in his slaves. Like the owner of working horses, he has an interest in their health and welfare. Also like the owner of livestock, the Capitalist slave owner was likely to develop a real affection for his slaves and feel great responsibility for their well being. But, the slaves were still slaves, held in bondage against their will.
Government slave owners, on the other hand, cared nothing for those they enslaved and often worked them to death knowing they could use the power their position gave them to simply enslave others. In many cases it was actual policy to work them to death. Both the self interested concern an individual owner might feel and the human interest one person might feel for another were absent.
In the case of poorer employees in third world countries I’m sure the concern for the employees demonstrated by management runs the gamut from the best of the antebellum South to the worst of Soviet Siberia. BUT, the slavery analogy breaks down almost immediately. Workers in Mexico and Thailand are not taken in raids or bought at auction. They must actively seek employment and are free to quit at any time. Certainly their options may be poor, but no law or force prevents them from seeking other employment. Without the jobs offered by John Bloor, and others like him, their options are limited to those provided within their own societies. Often very poor indeed.
The only real losers in this scenario are workers and governments in high wage welfare state countries. American workers are the most productive in the world. But if wages, benefits, taxes and price them out of the market they will lose out. The people who live in low wage low tax countries are only too happy for the work. Even if they work for a fraction of what an American or Briton makes they are usually among the highest paid workers in their countries.
Europe, especially France, has tried to become a leisure society. But if you won’t work more than 35 hours a week, demand 8-10 weeks of paid vacation every year, pay generous benefits to those who choose not to work and still expect to live a prosperous life, you shouldn’t be surprised when the hungry and hard working take away your markets.