Shorter version of vegetarian post:

It's too simplistic to assume that the valuation of life can be maximized by forswearing the use of animals in the diet.

And it's certainly way to simplistic to assume that the ecosystem can be tuned to maximize the amount of animal life by forswearing carnivorousness or omnivorousness.

The latter, in particular, got us through the Cretaceous–Tertiary extinction event. Of course, "we" were shrew-like creatures, but still...