People aren't going to start keeping the equivalent numbers of livestock as pets. If factory farmed animals fall out of fashion, most of these animals will all die without reproducing and their bloodlines will cease to exist.

I agree that factory farming isn't ideal, but it seems to me that it is less ideal from the perspective of the animal for their entire bloodline to be terminated. To make a strong argument against factory farming, you have to provide a feasible alternative that IMO doesn't exist.

The question really comes down to whether or not you consider the opportunity to experience life, even a particularly difficult life, as a blessing.