Humans have evolved on the basis of being able to cook. We essentially used to have a second stomach. The appendix, it would help us digest all the grass and whatever else we'd eat at the time. Since learning to cook however, the appendix basically stopped being needed and gradually decreased in size until it became a useless thing that can occasionally try to kill is. It's just evolution. The "natural" thing for us to do now is to cook. So the raw meat argument is invalid.
Don't get me wrong, I'm vegetarian. Your argument is just stupid.
Edit: Just wanted to add vitamin B12 as an example. It's very common in grass and animals that eat grass. We used to eat grass ourselves back when the appendix was actually useful, but since learning to cook we started getting it from eating the animals instead. Without meat (or at least milk), there's actually no "natural" way for us to get vitamin B12.