Don't see them going out and trying to convert tigers/sharks/etc. to be vegetarian/vegan. They'll probably get chewed alive!
Such arrogance to assume us humans are "above" being animals when in reality we're pomped up hairless apes. We ARE animals, no ifs or buts. The only difference between us humans and other animals when it comes to obtaining food is that we've got
really bloody good at it. We have the technology to wipe out entire species very quickly for food, and learned methods to sustain it if needed (ie. cattle farming). When it's pointed out that the way we do it is "unnatural", it really rings alarm bells in my BS meter. What we do IS natural as we gained our ability through natural means. After all, it all stems from making tools to help us defend ourselves from other predators. To be unnatural would be to fabricate shit with black magic and conjure up the undead, or something along the lines of that.
I will bet you that if any other animal that evolved to the level of intelligence etc. we humans have, they will most likely do the same. Some of those animals will then become vegetarian/vegan for wanky political reasons, try and convince others they're wrong and that they're not supposed to eat meat. Both will bicker and moan at each other. You get the idea.
On a somewhat related note, I found an excellent quote. I like to think it refers to the possible result of humans trying to censor/ban etc. for their own political agenda in order to make a "better world":
"1,000 years from now there will be no guys and no girls, just wankers. "