Just talked with a friend (thanks, Sarah) about the manifold benefits of a phytocentric (plant-centered) diet, not just for individual health but for the health of the planet and the welfare of other earthlings. But even these all-pervasive benefits neglect what is perhaps the single biggest plus that plants bring to one's life, which is spiritual.
The ancients say that eating animal foods increases animal tendencies, which tendencies (lust, greed, anger) then increase cravings for animal food. The mystery is, how to stop this vicious cycle - is it by changing a person's diet so their cravings will change, or does what need to change first is a person's consciousness? That's an awkward sentence for a confounding issue.
On the spiritual path (and all humans are or should be on that path, as self-realization is the ultimate purpose of life) vegetarianism is absolutely essential, so whatever gets a person there (looking better, feeling better, more energy, etc.) is well worth the effort and justifies the end. Some people can't see it. We all at one time or another "wear blinders or some kind of filter over our eyes," so use Sarah's aptly-chosen words, but rather than seek to change the world, be the change you wish to see.
It is true that what matters most is not what goes in your mouth but what comes out of it. You can be as pure as a breatharian but if you are a gossip monger who tongue lashes people then this could hardly be called clean living. But the two (diet and consciousness) do influence one another, and eating beasts increases beast-like tendencies within us, while sparing them in favor of nutrient-dense phytofoods is the nonviolent approach that changes you, and by extension, changes society, bringing peace, which we all could use more of.
Of course once you are realized, once you become a sage, then you can eat whatever you want, according to the holy man Ramana Maharshi. When the fire of universal love burns so bright, it doesn't matter what you use for fuel. But by then as now, you'll find old habits die hard, so choose plants.