I think it's a valiant attempt with some major blind spots. He bases his argument on the premise that omnivorism is believed to be unethical (i.e. traditional PALEO is unethical) because it results in the death of animals. He then argues that if you accept that premise, you should also believe that being an herbivore is unethical because everything we eat (veggies included) results in the death of animals one way or another. One example: farming razes fields, killing cute little gophers. http://www.marksdailyapple.com/is-eating-meat-ethical/#axzz1r66vf5dG
I don't think being Paleo is unethical, but I do think Sisson misses some big points:
(1) If you farm your own veggies, or find small, environmentally responsible veggie farms, this could greatly reduce or even eliminate animal killing (ants totally do not count, I assume we're talking about relatively sentient beings).
(2) The premise could be inaccurate--it might not be the death of animals that is the root of ethical questioning, but rather, the sheer magnitude of the animal deaths or the mechanisms by which they die. So, for example, veggie farming might kill animals, but eating meat kills more animals. So maybe it's considered to be unethical because you aren't reducing impact when you could be, NOT because there is death per se.
What do you think?
[EDIT: I think this post has drifted into areas already covered by other posts (my bad!) we should probably close it (needs a moderator or three more votes). Look here for posts about ethics of paleo: http://paleohacks.com/questions/9826/paleo-vs-vegetarian-a-question-of-optimal-health-vs-evolved-compassion#axzz1r6SYVgbI).]