Then, when you try to legislate any kind of standard for humane livestock treatment, the farmers throw a hissy fit and block all the roads with their tractors.
It's not possible to produce the amount of meat needed to feed our massive population while treating animals humanely.
There are really two options to deal with this:
Most humans in the world become vegan -- sounds great but it's not gonna happen
Reduce our population to sustainable numbers (by eliminating the driver of the population explosion, i.e. fossil energy) -- maybe also not gonna happen
Edit: What (do I think) will happen? We'll continue as we are now as hundreds of billions of animals are tortured until our civilization collapses. This will happen because we were all brought up under a state and told that defending ourselves, our communities, our animals, is wrong and illegal.
False dichotomy here. Americans could certainly reduce their intake of meat without going full vegan. Regulations could be created to treat livestock more humanely without completely eliminating factory farming, which yes would increase prices, which would probably also reduce meat consumption somewhat. Also population growth within the US has dropped off quite a bit and is projected to further decline.