But whatever you call them, targeted killings or assassinations, under the laws governing Occupation, they remain unlawful under international law unless the individual was participating in the hostilities when he was targeted and killed. A sleeping man is not participating in any hostilities.
Every human being, insect, plant (however subjectively undesirable) is necessary. Maybe that concept would be too far rooted in philosophy to be reality, in some people's opinions.
We are the....master (for lack of a better word) of our body. When infection invades, our immune system combats the bacteria or other undesirables. When cancer attempts to take over, we fight it with drugs. These two instances are an example of smaller forms of life, attempting to upset the balance of nature within us. When the infection or rogue cells win the battle, the body dies; and everything within that body dies as well.
To me, this is similar to the balance of life. If we, as individuals, attempt to defy the Master-whoever He or It is-by exterminating an entire race, leveling an entire forest, mining mountaintops, or whatever...it upsets the body, of which we are possibly a small part of. Nature will fight back, or we will ultimately "kill" the body, and kill ourselves in that process of playing, the master. Think homeostasis.