While I'd readily admit that the average vegan probably has a much healthier diet than I, I don't think this is any sort of good argument. I'm fine with you using it to justify your being vegan, but considering an equally healthy diet is easily possible without the vegan restrictions, I don't think it (unless you suplement it) is a good argument.
Please note that throughout the thread, I've tried not to push a vegan agenda. I didn't say not to eat meat/milk/etc, I've said to not eat *much* of them. Although I don't agree with eating animals, I know that others don't take the same stance. That's why I promote a healthy balance.
My point has really been, animal protein has been shown to cause bad stuff. Period. The rest has been arguments about language/other side-channel issues.
If the human body was not designed to consume meats, you wouldn't have the various enzymes that facilitate the absorption and decomposition of meats. They would, like certain poisons and chemicals, go through the body unchanged and instead be poisonoustoxic ((yay i remembered the word i wanted to use!)). Additionally, you would have no use for the canine and incisors that have been evolved into the human mouth.
I am (obviously) not a doctor, but I do know that the human body has trouble metabolizing meat. Yes, we can break down meat and absorb it, but so can herbivores (cows come to mind -- they're frequently fed meat (each other) on farms). At the same time, my understanding is that, like herbivores, we have longer intestines that work well for vegetable matter, because we're able to extract the maximum amount of nutrients from it. Meat, however, begins to decompose because of the length, and that's why it raises your risk of colon cancer and such things.
I haven't done any research to confirm or deny any of that, but it's my understanding from potentially biased sources.