I appreciate your willingness to take on a difficult article. In essence, you are responding to Newman’s response to an argument he had with a vegan, and this discussion is very nuanced, since he is talking about the thought process and worldview of his opponent rather than making straightforward arguments against veganism. It would be difficult to capture these nuances in a short article, but your was piece made an admirable attempt, and I think it helped you express your own position effectively: the vegan worldview helps promote the ethical treatment of animals whether you decide to practice it or not. Newman’s thesis was slightly different: Vegans care more about animals than they do about environmental conservation.
From just this distinction, we can see that it an extremely complex topic. Right now, vegans are a fairly marginalized group with little impact for good or ill on the ecosystem or the global domestication and use of animals. While I wouldn’t have expected you to respond to his argument point by point, spending just one point to debate in specific detail might have made for a more focused and effective response.
I notice that you started off this way when talking about the animals who are killed by modern farm equipment, but then the second to the last paragraph tends to get a bit off track. It starts with the incidental killings but then diverts into the problems of fertilization and food waste. When we come back around to the conclusion, we have lost the thread of the ethical treatment of animals, and it almost gets lost there. You already have a strong tendency towards civility and understanding, so don’t afraid to make your own opinions more clearly and forcefully.