Fwiw, the general vegan philosophical position is that factory farmed animals should not exist in the first place, regardless of numbers, and this is due to the primacy of suffering as the chief evil in the vegan mindset.
It's not such a terrible general principle to apply to humans either, and we do it routinely.
So I think Larry's argument (if I understood it), is essentially correct, there is an inconsistency in those statements.
Animal suffering not caused by humans is a thornier matter, though, and may go some way to explain some AR activists releasing animals into unsuitable conditions that they deem "the wild", in order to meet a drawn out and grisly death.