I think the only time it might not be inherently awful is wishing someone who is currently murdering people/torturing/whatever were dead so it would save lives. It isn't about that person, it is about the lives saved. But even then it makes me uncomfortable. I just think it is pretty shitty to wish a real human being were dead. They are a person. They may have done awful things, and it is okay to hate them. But wishing them dead? I personally don't think that is okay.