The problem is most people jump into diets like vegan, vegetarianism, carnivorism, etc without having ever experienced a healthy, balanced diet. If you ever experience a healthy diet, you will know the differences between them and those fads.
People going into vegetarianism and veganism, for example, have never eaten enough vegetables and other plant products before. So, of course, they feel the benefits of having a healthier amount of plant products in their life. They will never, however, feel the benefit of also having the proper amount of animal products in their diet, and ultimate damage themselves. Something similar happens with people on carnivore diet.
You're free to make your choices. Just don't push unhealthy diets here, especially when you've never eaten a healthy diet before. You will never sway smart people that way. As you advance, contrary to what crazyblue said, you will notice that something is wrong with an incomplete and thus unhealthy diet. You may not understand that your diet is what is wrong, unless you keep an open mind about things.
What diet works for you is individual. However, it's never found in extremes. Both animal and plant products are essential, as that's how human beings work. Some say they become a certain way because of ethical and moral reasons, but they are actually at a lower understanding of ethics and moral. They don't really have the moral high ground they think they have. They only have arrogance, brainwashing and lower, unrefined expressions of Neptunian and Piscean energies (in the case of vegetarians and vegans) while it's similar mismanagement of Arian and Martian energy in the case of carnivore diet.