Sounds like you're valuing <mean harm per animal> over <integral of harm over all animals>?

I don't get why that would be a better measure?

This gets into a deep philosophical question people spend too much time arguing about. In short, some would argue suffering is multiplied by the number of sentient beings that experience it, others would argue only the average "amount" of suffering matters. You can end with some absurd paradoxes if you take either to their extremes.

The reality is probably somewhere in the middle.

While this entire chain of thought seems a bit far fetched, I think the reasoning here is that if you lower the demand for meat, you don’t have to resort to factory farming.

It also reduces the number of animals that suffer if the suffering is more important to your ethics.

I suppose thinner people do probably walk their dogs more often…