Actually in that show I watched, it said something about meat leading to cancer just because humans can't digest it very well and it sits in your digestive tract in a warm environment. And I COULD see how something might lead to cancer that way.
Man, this show mapped out an entire diet that prevents most of the diseases we have today (type 2 diabetes, arthritis, heart disease). It's called "Forks over Knives" if you want to check it out on Netflix.
People are dumb about that. I get WAY more protein than anyone I know each day without eating meat. I drink a lot of whey protein shakes. But I'm also making sure to eat a lot of nuts, beans, etc. It's true, though, there are a lot of dumb vegetarians out there who don't make the effort to make sure they are informed about their protein options and don't get as much as they should.
I watched somewhere that vegan and vegetarian diets are much healthier, especially in warmer climates. I've wanted to switch over so bad but my grandpa keeps getting on my case about how "I won't get enough protein". Stupid faulty science. :/