No, it isn’t. From the Essay in clear terms: “I will argue that if vegetarians were to apply this principle consistently, wild animal suffering would dominate their concerns, and may lead them to be stringent anti-environmentalists.”
The weak axioms on which this essay is founded can be easily highlighted by editing it to be an anti-abortion essay instead of an anti-vegetarian essay.
Anti-miscegenation laws - Wikipedia
I think that the author of this essay has deliberately confused readers with his terminology, particularly by avoiding the term ‘vegan’. That may explain the confusion in the comments. For the purposes of his arguments, Thomas Sittler suggests that what he calls ‘vegetarians’ are environmentalists. In fact he is talking about vegans, and they are not environmentalists at all, and increasingly they are anti-environmentalists.