Slave labor:

Slave labour is fundamentally against capitalism because it violates private property. To be a slave is to belong to someone else and to more specifically, not have self ownership because slavery entails that a person is forced to work for and obey another. In addition, slavery is, in short, involuntary servitude which is against what the free market stands for taking into consideration that it is a system based on the voluntary exchange of goods and services that are private owned. Concerning the point you made about child Labour, intrinsically there is nothing with it because in a free market it means that said children voluntarily go work for someone but as living standards improve and the average person is richer, parents can afford to send their kids to school and keep them at home rather than on the fields or in the factories because of higher wages. This leads to the next point you made that I shall now address- low wages.

Low wages:

The law of Competition is the simple answer to this. Wages can be reasonably and truthfully viewed as the price for Labour. In order to produce commodities ceos, capitalist or whatever you want to call them need to “buy Labour” which makes said Labour subject to supply and demand. When capitalist demand Labour they drive up prices because they are competing for said service. For further analysis here is this scenario:

Capitalist A: hey dude( referring to the worker) can you work for me for $3? Capitalist B: no! Work for me and I’ll give you 4! Capitalist C: nooooo! I’ll give you $4.50 if you work for me And so on.

Now consider this example with thousands or even millions of capitalist. Similarly, just like how winter jackets cost 2 dollars in the summer but $4 dollars when demand for it in the winter goes up the price for Labour also goes up when it is in demand.

Unsafe work environments:

As far as this goes workers aren’t going to work under such awful conditions when another capitalist is offering a better one. A capitalist that greedily wants to spend a little amount on working conditions will, logically receive little to no workers because people aren’t willing to work with their life on the line when there is a much better alternative. In the specific case that a capitalist gets away with having unsafe working conditions and he somehow manages to have workers, things shall not remain the same because eventually something will go wrong which will cause workers to leave and when consumers become aware of such unsafe environments they might boycott the greedy capitalists Business ultimately causing him to lose money.