saying something makes no sense to as a rebuttal is an argument from personal incredulity. My argument is right now in our stage of technological development, its not a viable option for every human to quit killing. Populations of species would go unchecked and ruin the delicate balance of the ecosystem. Please show me how there are enough nuts and berries to support the entire world population. Fights would ensue over the limited resources, we would have to farm more, which is also harmful to the environment. Sometimes, attempts to save the world only makes more problems. Who are you to question tens of thousands of years of evolution? For some, they think its selfless to cower to their empathy in order to avoid feelings of guilt. They would rather cause greater harm to the whole, so they can feel better about themselves for protecting the lives of individuals. Its a god eat god world, its only sad when you focus on the individual perspective. Life eats life and life continues to manifest itself in countless ways because of this process.
To counter my argument, you would need to show there is enough non-meat food source to support the entire world population without additional farming. You would have to explain how we would keep ecosystems in check without its apex predator thinning out the numbers.
Like I said, veganism is a beautiful moral high horse. But, to say that we as humans should not eat meat is naive and short-sighted.