Forcing someone to work for you isn't allowed, but paying someone to work for money so he doesn't starve is totally accepted.
This reminds me of this :

Working 9-5 day job with the same boring routine and for others to make them rich just to get a part of it with all the burden is for sure most distrubing form of modern slavery.We thought slavery was past concept but the system never removed it but just developed new ways of it which still many don't understand.
The problem with this line of reasoning is that the most intuitive solution is: All means of production, not only labor, should be in the hands of the laborers. That's communism, or some variation thereof.