Building upon your metaphor…
In order to have leverage the laborers need a fulcrum in the form of alternative employment. Otherwise you are just moving them from abused and hungry to unemployed and starving.
That only works if the laborers have a viable plan B. If the alternative to a dangerous, dirty job is something worse, you’re not doing them any favors.
I find that purely practical arguments without any political litmus tests are much more successful. My last summer road trip was 1,500+ miles with an out of pocket energy cost of $49. (Plus some free hotel charging.) That gets the attention of any hard core capitalist.