I'm in agreement with you. People do tend to go to extremes when they jump on a diet wagon. Most health people who are aware of the benefits of a plant-based diet tend to discount meat altogether. While I agree we eat way too much, I'm not a purist.
I was glad to see that at the end of his book, Eat for Health, Dr. Fuhrman summed up the scientific literature that he'd read on meat & vegetarianism. His conclusions were, in short, that while vegetarians experience much better health than those who eat meat 2-3x daily, they do NOT experience much better health than those on a plant based diet who eat meat about 3x weekly. His belief was that this is because the vegetarians ate more veggies. His emphasis (and this makes total sense to me) is not what to absolutely avoid or include but is based specifically on making most of what you eat high-nutrient density food. This means mostly plants whether the minority of your diet is meat or not.
Apparently vegetarians must supplement with B12. I'll just have some chicken salad & shrimp now and again. :-)