"From the animal standpoint, leftists have been regressive and reactionary forces. In the Communist Manifesto, for instance, Karl Marx and Friedrich Engels dismissed animal protectionists as mere petit-bourgeois reformers. They failed to see that the animal welfare movement in countries like the United States was vital to women whose opposition to animal cruelty was inseparable from their struggle against male violence and the exploitation of children. Similarly, in his work, On the History of Early Christianity, Engels belittled vegetarians and anti-vivisectionists, with no understanding of the importance of these issues for reducing human cruelty to both human and nonhuman animals, and for moral progress generally."