They provide shitty jobs for a lot of desperate people. If we don't work towards a world with good working conditions, we won't work in good conditions.

So did slavers, or parents wouldn't have agreed to sell them their children.

That is assuming those employees aren't desperate for work. Had we adequate social welfare, or a glut of unfulfilled good jobs, I might agree, but when your choice is "die or work at the level we want", they aren't really given a real choice.

This is incredibly naive (or disingenuous?). When the alternative is just not having a job people will take a lot of shit, that doesn't mean it's okay.