Some animal byproducts simply aren't good for you. Eating the ass off a cow is tasty, but there is no way that should be your diet.
Drinking milk is something that human's shouldn't do either. Last I knew, there was nothing in nature that taught us to suck off the teat of a beast.
Also, when it comes down to it I was brought around when my dad had his heart attack - The doctor told him to cut down on the meat and milk. So my question was : "Why should it be there in the first place?"
In defense of Meat: Humans started eating bits and twigs that they gathered on the forest floors. Berries and veggies. That was all we pretty much did like any other animal: Reproduce, eat and sleep. When the first human killed another animal, they managed to eat for weeks, get their protein and nutrients, and spend time doing other things like building Fords. Meat is the key to society.
In defense of being a modern vegetarian (Of which I'm not): Humans are omnivorous, yes. But if we were really meant to eat meat, why do we need forks and knives ? I mean, other meat eaters don't. Our teeth aren't made for eating meat, and our bodies aren't strong enough to rip into a carcass.
In defense of the overal jist of things: We are evolving. And if our bodies begin to take us away from eating meat, then I say let it happen. If meats are giving you gastric distress, a belly, really bad odors and causing hair loss - then fuck it, don't eat meat. Maybe it's your body trying to tell you something ! My suggestion for everyone is to cut down on the meats that you eat, except Fish. Not enough people eat fish (And if they did, populations would be wiped out within a few years). Just cut down on it, and you'll begin to feel something - whether you're sicker or healthier. If you're sicker, then adjust.
There shouldn't be overall rules out there for eating meat. Like "You need two servings of beef everyday" or some shit like that. You DO need a specific amount of vitamins from vegetables, but meats offer corollaries to that rules.
When I was living in NH I was too poor to afford meat. Pasta, veggies and lots of walking (To work and around town) made me feel absolutely great. Now though, I eat meat for that energy boost that keeps me going (And I gained 3 pounds. hah.)
We will, as evolution points out, begin to eat less and less meat. Which overall is good because it's easier to maintain the footprint of a corn crop than it is the walking grounds of cattle. Also, Cattle tends to eat a lot more food than it provides, which is a system that can't maintain itself.
And without government farm subsidies, a hamburger would cost $20.