Murder is fucked up, human or not.

Couple issues with that. Murder is just illegal homicide. The homicide bit means it's definitively only dealing with humans, and the legal bit is only as fucked up (or not) as the law itself, and history is littered with examples of legality clashing with morality.

We have some really evil folks in this world and they're protected by the same laws as everyone else. Some of those evil people are doing things like running countries or mega-corporations or engaging in some other means of causing a massive scope of death and/or suffering. You find yourself in a position in which you could feasibly take their life - do you? It's illegal: very much murder. But allowing them to persist allows whatever evil they're inflicting on everyone else to also persist.

I know none of this is what you're talking about, but I see the word 'murder' pop up a lot in conversations like this, and it's just not the correct word for what you're trying to describe. You can make a solid case for the morality of veganism without relying on the connotation of buzzwords that aren't actually relevant.