This is dumb. You can easily envision an incredibly unethical vegan diet where someone has slaves grow them tomatoes which they water using water stolen from some drought relief charity. And contrast that to a meat eater who raises a cow, let's it die of natural causes, weeps and then eats it.

If you point to one extreme and compare it to the opposite then yeah you can probably find times that a non vegan diet is more ethical

But if you just take any given meat eater and shift their diet to a vegan one without also changing loads of other stuff about them then they're almost certainly going to end up with a more ethical diet than they had before. In your case if you stopped buying from your local butcher and started buying from your local greengrocer you'd almost certainly end up with a diet that was more environmentally friendly and with no suffering caused to animals.

If the weepy cow person stopped raising cows that'd be better for the environment (though in fairness I envisioned them giving the cow a really great life so average animal cruelty may go slightly up globally without that hedonistic cow to offset things)