It counts as political because you're talking about the deservedness of rights for a social group (animals) that would be costly for another social group (humans) to recognize. As a question of "who deserves what social status/share of the pie", it's about politics.

Second, a lot of problems you point to necessitate discussion of political issues. Specifically, when you talk about animal farming methods being bad because of the negative environmental costs they impose on other humans ("negative externalities") (which I completely agree should be internalized), you're on a topic that necessarily involves discussing a political solution -- i.e., who deserves compensation for these acts, what can rightfully be done to prevent it, etc. (To get the environmental benefits you describe, you need massive action an enforcement, not a few people's personal abstinence.)

So, other than the personal health benefits and personal moral choicemaking you discuss, I have to conclude that your post counts as politics, but that could be fixed by removing the problematic issues I mentioned in the preceding paragraphs.

(Just found this discussion.)