Report them to whoever is overseeing them

If you’re in the states, call OSHA and report them. Also have him file complaints with anyone he can. That is utter bullshit.

What kind of shithole of a job is that??

How has he been forced to quit (I am presuming an environment has been made which is unwelcoming)? If that is the case then I am presuming they made the same excuse a company made with a friend of mine, he was working to slow because he wanted to put the guards down on the machines etc.

If he has not reported the unsafe work conditions, then he is just an asshole. Sorry,no other way to put it. What, he leaves and whines about having to leave because it is unsafe but leaves other people to work like that? Are you kidding? Either man up or shut up. Unless he is going to do the right thing and report them, his own fault

Here in Australia there's a thing you can claim called "Unfair dismissal.", if you have something similar where you are, I'd do that, his former boss could get into a world of trouble for firing someone for doing the right thing.

he should've made them fire him. but have him call osha

Report them to OSHA. It is illegal to fire someone for following OSHA safety laws. It is also illegal to fire someone for reporting the company to OSHA