razbry, I wrote up a response yesterday but decided not to post it. But since you asked...
I haven't listened to the podcast (but I enjoy Milt Rosenberg's show and will try to listen to this one soon). Thanks for posting it.
I have no doubt that some line cooks are treated badly and many of us would feel bad about patronizing some restaurants if we knew more about what went on behind the scenes. But, on the whole, line cooks are not paid badly within the restaurant industry. Yesterday I pulled data from the Bureau of Labor Statistics about the earnings of various jobs within the restaurant and bar industry. These data aren't perfect, but they are the best we have (and, yes, they include tips for those who receive them).
The data show that average hourly earnings within the industry range from about $8.80/hr for dishwashers to a little over $20/hr for chefs/head cooks. Cooks in restaurants make, on average, about $11/hr. Short order cooks make $10/hr. Fast food cooks make about $8.90/hr.
Waiters make about $9.85/hr. Busboys make a little less, about $9/hr.
These are averages and naturally some people make more and others less than the average. But if you look at the highest 10% of each occupation, or the lowest 10 percent of each occupation, the ordering of salaries across occupations is the same.
So the point I'm getting at is that the data don't bear out this idea that line cooks are the lowest paid group in the industry; far from it. The data list 17 separate occupations in the industry; cooks are the 5th highest.
"Exploited" means that they are being taken advantage of or being dealt with unethically. I have no doubt that this happens. But I don't think it is endemic to the industry. Nor do I think, when it does happen, it happens more frequently to line cooks.