I was a strict vegetarian for many years and it absolutely wreaked havoc on my health. I really think that a healthy diet is a very individual thing. What works great for one person may be recipe for disaster for another.
I was a "good" vegetarian. I ate a great diet- whole grains, lots of fresh, organic vegetables, and always a good source of protein. During a good part of this time in my life, I even managed a natural foods store.
Overall, I was a vegetarian (and a vegan for part of this time) for the better part of twenty years. I developed diabetes, high cholesterol and blood pressure, and had crippling migraines. As I began to add meat back in slowly, my health improved and has continued to do so. Do you know how hard it is to be a vegetarian diabetic? LOL. For me, it was impossible. I still haven't eaten any red meat or pork for more than 20 years. My diet is still vegetable based, many of which we grow ourselves. I have added back in eggs, cheeses, chicken 2-4 times a week, and fish a couple times a week.
My health has totally turned around since going back to "some" meat. As always, your mileage may vary.