Vegetarianism is not healthier. We are omnivorous, and about the same as black bears. Black bears mostly eat fruit and veggies, but do eat meat when they want to, because there is a lot more protein in meat, as well as useful fats, vitamins, and minerals. It's not unhealthy, but it's not healthier. It's just different. If you are a vegetarian, and have been for years, then it will be unhealthy to just start eating meat again, but that's a different problem (your digestive tract can't handle it). But because meat is loaded with much more energy per gram than just about any plant matter, it's the most efficient way for us to get our energy needs.
I don't see it as causing harm. It's just life to me. I mean, I can see why you view it like that, and I understand (I'm fine with it, btw, it's your choice, I don't really care), but to me, meat is delicious. I'm not going to give that up just because some animals have to die. Besides, there's some things you just can't cook without meat, and food is glorious. Animals just don't have the sentience with a few exceptions (there is a test, and so far very few animals, and no staple food animals, have passed it) for it to be immoral to me.