To me that's more ethical than killing of billions of animals, and the latter is considered ethical.
I think most people would actually consider factory farming unethical, they just put the blame on the producers for treating animals like shit. And the producers are locked into a race to the bottom for competitive prices, so they'd blame the customers/market conditions.
It's so despicable that society punishes kindness whilst rewarding greed. Common sense tells us that it should obviously be the other way around, yet it isn't.