What trait absence in animals that if absent in yourself would make you disregard your right to life? You might say retardation but you would be too retarted too know there's something better if it happened at birth. If someone tried to kill you I'm sure you would put up a fight even as a retard. I'm not saying veganism is a must for everyone as everyone is on their own path but it is somewhat of a zietgist as it is the logical conclusion to how we want others to treat us. Man acts in his own self interest and therefore we protect it.This statement "man acts" is something we can all know before experience or what's called in epistemology a *synthetic a priori*. To argue that man does not act is to prove that man acts in the act of the rebuttal. This is what's know as an axiom. From here this is how we can start deriving norms like private property and freedoms. We haven't figured this out yet for people let alone animals. Some people are farther on the path then others but it's important to know how we know things and how we can prove things through logic, even if it seems purely empathetic.