(Inspired by posts on The Corner in National Review)
Ask any vegetarian WHY he is so, and the answer's likely to vary. Some people decide to swear off meat for health reasons, or perhaps on doctor's orders, in which case I can only salute and wish them the best. Others say that they have no particular reason, they just prefer the taste of soybeans and vegetables or don't like the tastes of meat--fair enough. A few, though, will probably turn the matter into a question of morals, citing something about "protecting animals" or "preserving life" or "it's natural for life to be non-destructive", etc. I'm not entirely certain I can get behind this, and here's why:
Thanks to the biological definition of "life" including everything from bacteria to various single-cell organisms (euglena, etc.) to plant life to mushrooms to sponges to sea cucumbers *deep breath* to cockroaches to chicken to cows to us, and the fact that the Earth is a limited sphere with attendent limited resources (even if humanity didn't exist), all life must invariably thrive on the destruction of other life. Plants, given the same area of land to exist in, will attempt to choke each other out and gain dominance. Predator-prey relationships provide an even more obvious example; as the predator thrives, its numbers demand more prey animals be sacrificed to hunger, until there isn't sufficient prey to get eaten and the predators start starving to death, which allows the prey to start reproducing again with reduced threat, which prompts the predators to eat, get healthy, and start growing again, and so on. Two predators with one prey will result in the predators killing each other, or at least forcing the other to starve, to monopolize access to the prey. One we add decidedly nonstandard relationships (single-cell parasites attacking plant life, or various diseases attacking the predators, for example) and get up to ecosystem levels, nature becomes a metaphorical bloodbath of species, each attempting to assure their own survival, usually at the expense of other species (there are a few symbiotic exceptions, but they're rare). What some romantic authors call the "balance of nature" is a very unstable equilibrium, likely to be driven out into massive cycles of starvation and overproduction by the next rabbit baby boom.
But we're sentient creatures, say the moralist-vegetarians, and certainly we have an obligation, moral, religious or otherwise, to avoid such destructive orgies. Perhaps so, but (a) that pesky biology definition means you're destroying life anyway to sustain yourself (and, in the case of nuts, seeds, fruits, and legumes, metaphorically ripping out plant unborn from their wombs for consumption, possibly eating the womb, too), and (b) your immune system is on autopilot and is killing everything that's not you on the off chance one of them will cause the unfortunate side effect of causing you to get sick and die.
It may be a beneficial or logical choice to kill our meat animals humanely (by executing them quickly and getting all the meat available to maximize investments rather than tearing off a piece with our knifes and leaving the bellowing creature for the scavengers), or perhaps to raise our own animals expressly for the purpose of slaughter so we don't have to go into nature and kill an elephant or mountain goat or gazelle or whatever to get food (which is how civilization got off the ground). Since life requires the destruction of other life, however, to assert that vegetarianism is inherently more "moral" or "closer to nature/natural instincts" than meat eating is absurd.
(Also, an anecdote from a colleague in college regarding Mongolian spiritual mediations on the matter:
A story from when I was hitchhiking across the Mongolian border: Mongolians it turns out pretty much only eat meat. The explanation is that every time you eat something you're taking on a karmic debt of killing a soul. A goat can feed you for a couple weeks and you've only killed one soul. It's completely mind boggling to them why anyone would want to be a vegetarian - the number of plants you're killing in such a lifestyle is way more than the number of goats they're eating.)
(Oh yes, I never answered the question in the title, did I? It's because, like the vegetarian who does not like the taste of meat, and thus chooses to be so, I do like the taste of well-prepared chicken, fish, beef, pork, etc. [well-prepared anything really], and choose to eat according to my tastes.)