Tough physical labor is not for everyone. For example, I would not last 6 months in a construction job (I easily get colds when I work outside). As long as the majority of people working in that warehouse are ok, then maybe your friend was just not suited for the job.
This is not just about tough working conditions. It's about the way management treats employees, and encourages employees to crap on other employees for small gains. Google "I was a distribution warehouse wage slave" and read that article. It will get you a better idea of what I am talking about.
