Serious Eats - seriouseats.com

"After reading it, I realized that I was in violation of those ethics even while being a vegetarian," Ms. Kelso said. "Unless I drop out of society, live in the forest, and become a hunter-gatherer, I have an impact based on what I buy, no matter what it is."

Putting aside the fact that factory farmed plant foods are still preferable to factory farmed animal foods from an environmental/humane perspective, the fact is that Pollan's book was written to make people aware of the problems of industrial farming and to encourage people to seek out more ethical alternatives for their food, be it animal or vegetable. It wasn't written to encourage people to say "screw it I'll eat whatever I like no matter where it came from". And if someone is eating spam musubi from L&L Barrbecue, they are indeed saying that very thing.

This is a good example of the "black and white" reasoning some people use to abandon vegetarianism--that it's better to do nothing than to do something that falls short of perfect commitment. The same reasoning that some people use for not recycling, guzzling gasoline, turning off unused lights etc. because anything short of living completely on solar power in the woods is not worth bothering about.