Why is Paul hesitant about showing sympathy for the Russian soldiers?

Here is a quote from GradeSaver that might help,

Similarly, Paul cannot muster true sympathy for the Russians because he sees in them only "the suffering of the creature, the awful melancholy of life and the pitilessness of men." He does not know the Russians beyond these generalities; as he says, "How little we understand each other." Such an understanding seems impossible under these conditions of scarcity, when each side wants to take advantage of the other for such bare necessities as boots and bread.