1- The lean protein in meat is much healthier than other saturated fats (saturated fats are harder for your body to digest). Vegetarians have to be careful and find safe protein alternatives, so it is a real challenge. However, there are other health benefits that come with this. Like lower chance of heart disease and body fat.
2- Totally true; People at risk for cardiac issues, people with high cholesterol naturally, etc. However, there are times when you have to eat meat. For example, I have a friend with crones disease, and it severely limits what he can eat. One of the few things he can have is chicken. So this swings both ways.
3- Moral restrictions on eating are really interesting. I have a lot of things I don't eat for religious reasons, and it is really hard sometimes. However, both for moral and religious reasons for changing diet, people tend to constantly try to change my opinion. "Well, why can't you have A, B, or C?" Because I choose to sacrifice for my beliefs. "But why though? That is a really dumb belief because..." And so on. Choosing to go against the standard is really hard, but it is always worth it because it strengthens your resolve every time you stand up for your self. I have mad respect for vegetarians.