What's right and wrong?

Both Vegetarianism and Omnivorism(?) are perfectly feasible dietary plans. But to fall into the "healthy" category, both plans need careful consideration.
Vegetarians need to eat a very mixed array of vegetable and legumes to ensure they satisfy their bodys needs in terms of vitamins and minerals.
Omnivores need to ensure they don't overeat. IIRC, the recommended daily serving of meat is 60-90 grams, yet the average steak weighs far more than this.

As a result of this, "healthy" vegetarians compared to the overall vegetarian population have a larger percentage when you compare the "healthy" omnivores to the overall omnivore population as vegetarians need more will power in order to sustain their dietary needs.