Regarding plants, I replied elsewhere in this thread as to why I think they aren't conscious, but even if each kernel of corn were as fully conscious as a human being, it would still be more ethical to eat them directly than to feed that corn to a cow and then eat it. The reason for this is because for every 10 calories of plant matter we feed to a cow, we get ~1 calorie of meat out of it. So by eating the crops directly we are killing 90% fewer plants, without even taking into account all the plant, animal, and human life being destroyed in clearing rainforests for cattle. Without even accounting for all the plant, animal, and human life that is being and will be destroyed by the climate change to which the rearing of these cattle is a major contributor.

Otherwise I appreciate that you can see that it's all largely arbitrary, self-serving, and this way of thinking is what has lead to every other atrocity in our history. I think we are capable of being better.