f.w. nietzsche detested vegetarianism because he saw in it a pity that denied the continuity of reality. in his view, people became vegetarians because, seeing only the christian model of the pre-ordained and eternal soul as the model of mortality, they feared death and thus were unwilling to kill others or animals from that fear.
more advanced philosophies, such as his, held that life is continuous and individuals are manifestations of something else, a direct contradiction to the christian view (in christianity, purity is separate from this world, and thus individuals are symbols or avatars of something, but not it in its only form). the animal i eat is real, but so is the source of more animals, and that is more important. thus i have no ethical objection to cannibalism or carnivorism.
however, for the most part, i prefer to eat vegetarian, because i don't want to encourage the idea that this world is here for human exploitation. fruits and vegetables grow naturally and with a little coaxing, can become consistent sources of food. taking it much farther than that is to change agricultural society from a method to a goal, and that's an error - such an unheroic goal would inevitably lead to decay of an insidiously subtle and profoundly patient nature, spreading like a cancer until it reached all levels of society and the individual, including breeding them into stupidity, before revealing its real intent.
see? there's that reality question again. man fires a gun at you, the bullet's real. you can deny it if you wish. nature is consistent and results will occur as ordained, no matter how many times you watch The Matrix or read The Bible.