If we had a free market is would regulate itself.
Careful there. Your implication is that when the number of deaths or lawsuits from tainted food exceeds some financial threshold, then the free market will put that company out of business. Yeah, that's probably true. But do you REALLY want to live in a society where free market decisions are governed by deaths and illness?
Frankly, I see the pendulum swinging both ways. For a period of time, people die, get sick and it's caused by some farmer or rancher doing what is legal. Voila, Congress makes (whatever) illegal. So people stop dieing. Then years or decades later, society completely forgets about all those deaths and illnesses. Then the start complaining about Govt oversight, and onerous regulations.
Personally, of all the things I want my government overseeing, it's the safety of the food I eat. Regulate away...go for it.