We're technically not herbivores either, considering we can't digest cellulose ... Within biology, humans are regarded as omnivores, and rightly so - we've been scavengers from the early days as we have the capability to digest both plant and animal matter. Today it's perfectly possible to live healthy on a completely vegan diet in a developed country if one makes sure to get all nutrients from alternative sources (especially B12 since we can't acquire it from non-animal sources), but we're not biological plant-only (or meat-only) eaters.
As for factory farming, it's horrible because of the drive to maximise output by minimising the costs, thus resulting in horrible living conditions and administering drugs to stimulate aberrant growth. It's nasty af, both in regards to animals and the health of the consumer.