Pursuant to a conversation I had at our departmental drinks night last Wednesday—by which I mean, a conversation I’ve now had with shockingly little variation about four-hundred times since I went vegan—I have decided to officially coin my first sociological theory:
Barnard’s Law: In any heated discussion between a vegan and a non-vegan over animal rights, the non-vegan will eventually begin listing his or her favorite types of meat (usually, though not always, beginning with bacon). At this point, the non-vegan has officially conceded that he or she lacks any compelling argument, but the vegan should probably give up on the debate anyway.
Example (rough transcription of this Wednesday):
Me: “…and that’s why I believe that the morally relevant distinction should be sentience, not species.”
Non-Vegan Coursemate: “The other night I had lamb with pears.”
Cf. Godwin’s Law
Alex V. Barnard - Sociology 
It’s a weird defense mechanism, and surprisingly common. Even as a sometimes-vegetarian who usually invokes health and sustainability arguments, I get this all the time. Sometimes just saying I’m in 2D is enough. I’d love for you to explore why questioning meat-eating is read by meat-eaters as such an assault.
It’s especially interesting for me because I virtually never bring up the topic. Obviously, it comes up that I’m vegan, but I never try to engage people any more because I just don’t have the energy to respond, for the billionth time, to comments like “Dude, cows just naturally need to be milked. Would you just let its udder explode?” So people ask me about why I’m vegan, then get defensive or change the subject when they actually get an answer. I can only assume that people feel intrinsically challenged on some level by veg/veganism, and therefore start conversations on the assumption that they need to defend themselves from an imagined attack.