A preemptive action today, however well-justified, may come back with unwelcome consequences in the future. And because. . . I've done this. I've ordered these kinds of actions - I don't care how precise your bombs and your weapons are, when you set them off, innocent people will die.
The only way to save a rhinoceros is to save the environment in which it lives, because there's a mutual dependency between it and millions of other species of both animals and plants.