People kill lots of other species. Is that justice? Is it because we cannot communicate with them? Because they have such small intelligence? Is it alright to kill a species with low intelligence that we cant communicate with? Contaminating the forests and contaminating the oceans. Stealing the lives of others. Is it because humans are superior? Any species kills anoter to eat in order to survive. But humans are different. When they feel that it is inconvenient they kill a species or even their own. Is it because we cannot kill humans because they are stronger than any other species? Is it alright for an even stronger speices to kill humans?

 There is a moralistic answer. An idealistic answer, Or even a boilogical answer. It is possible to come up with many different answers. But whichever one you choose, it is not perfect.

 Why cant we kill humans? That's because people who cry exist and thats not only humans. When a living thing dies, there will always be others that are sad. Do you feel sad when someone dies? If it was a stranger or not even human. When someone dies, there is no one that wont feel sad. Even if it's someone they know, or dont know...they will mourn.Thats why we shouldnt kill. 

- from X/1999