A lot of people are eating less if no meat for various reasons. Besides the way animals are raised, what they eat, empathy for, perceived or real health reasons, use of water (a pound of meat requires between 6 to 20 times more water than a pound of cereal)... I am sure there are many more.
But here is a piece in the New York Times defending the ethics of eating meat. It is only fair to hear both sides, so check out this link