Look, i'm aware we have to kill to survive. I'm preaching at this point, but why stop now?
I just believe we consume far too many animal products. Part of my day job is schmoozing business owners, so I sometimes indulge in eating meat and poultry because it's customary. I do eat meat but not regularly. Once or twice a week, opposed to once or twice a day like I did when I was younger. When i do usually fish and occasionally frog legs

this is because of the reasons mentioned above but for other reasons too.
A large portion of the crops we grow go to feeding animals we are raising for slaughter. It's impossible to get an exact measure but it's estimated that if everyone went vegetarian we would have enough food to feed all of the humans globally 2-5 times over. This isn't realistic, ideal or desirable but even a slight reduction would help. Because the animals we eat are warm blooded, they expend a large amount of calories just by existing and maintaining body temperature. Because of this The caloric return is low. The estimates are all over the place depending on your source but it takes between 3-10lbs of feed per pound of red meat.
The US is improving by using soy husks and corn waste from distilleries for feed. Products inedible to humans. But this again doesn't help with the nutrient composition and health of the animals. If we only fed food sources non edible to humans (grass fed, etc) it would help negate this.
Pollution is another factor. In the book freakonomics by Stephen dubner and Steven levitt they examine recent studies that report the following. Ruminants produce massive amounts of methane. Ruminants ferment foods in their stomachs resulting in this gas. Cows and goats (the most common globally consumed meat) are Ruminants. Methane is around a 25x more destructive greenhouse gas than CO2. Again estimates but with all of the cows and goats domesticated on the planet they produce enough methane to equate to the amount of CO2 produced by combustion engines and factories globally.
With earth approaching human over population, we may be forced to cut back on meat consumption to combat famine.