I am not a vegetarian or a vegan. There are nutrients in animal products that are impossible to get in plants in any appreciable form. Examples being, vitamin B-12, and fat soluble vitamins A, D, and K-2. (note: beta-carotene in orange produce is NOT vitamin A aka retinol. beta carotene has to go through a complicated conversion process in which most of it is lost, and it's even harder to convert if you have certain medical conditions.)
I do believe it's possible to be a vegetarian and be in good health if you regularly consume eggs and full fat milk, preferably from pastured/free range animals. Some bone broth would be even better, but I know that's blurring the line a bit.
Dr. Weston Price, a dentist and himself a vegetarian, traveled the world in the 1930's searching for a culture that consumed no animal products. He couldn't find any. In fact, the healthiest tribes consumed fish as their main protein; followed by the meat-eaters; and finally the "least" healthy, although MUCH healthier than industrialized societies, were the primarily vegetarian agrarians (they still consumed eggs and some dairy though.)
I understand the concerns about animal welfare and the environment. I find factory farming horrific and disgusting, as do many people, and I refuse to support that industry. Vegan and animal RIGHTS (big difference from WELFARE) activists pretend that there is no other option, but there is. You can still buy meat from animals that are raised AND slaughtered humanely. I know there are those who believe that animals are equal to humans, so eating them is wrong, and for that I have no answer. ...Actually, I do, but it's a little long and complicated to post here.