1- Eating animals mean you eat more plants and use more resources (water, land, etc) than if you don't.
2- The environment suffers a lot from meat production.
3- Most people can live healthily on a plant-based diet, when done properly. Any diet can be unhealthy if you don't eat well, including veg diets.
4- Things like blood types and diet is rubbish, it's been criticised a lot. I'm an O and my blood tests were the best when I was veg, anecdotal.
5- Fat can come from good sources like oils, avocados, nuts, seeds, etc. You don't need a lot of it. Look at any country's food pyramid, it's a small quantity.
6- Iron from plant sources are more easily absorbed when eaten with vitamin C rich foods.
7- Eat food your great grand-parents would recognise, less processed, more natural.
8- Carbs aren't bad, just avoid refined. People in Asia have a lot of rice and aren't unhealthy (Japan has some of the longest living people). It's silly to base the fear of carbs on a fad diet (Atkins).
Also, I recommend to read The China Study or look it up at least, he found much links of diseases with animal products.
The China Study - Wikipedia, the free encyclopedia
Honestly, with a few quick Google searches you can easily find all the info. It's easy! Some keywords: environmental impact meat, vegetarian fats, the china study... Just try.