So this is what demons actually do: unleash the latent evil that exists inside human beings. Persuade them to give in to the devils on their shoulder, as it were. She wonders how she feels about this. Probably she should feel outraged, like the Order clearly does. But Hermione has not had the sort of life which permits her to maintain many illusions about human goodness. Adults can be cruel, and children are crueller. Have been crueller to her. It isn’t as though demons force humans into being monsters – they manage it all by themselves.