The world is simply not put together that way. Robins eat worms. Thats not fair to the worms. Spiders eat flies. Thats not fair to the flies.
Cougars kill coyotes.
Coyotes kill badgers. Badgers kill mice. Mice kill bugs. Tornadoes, floods, tidal waves, draughts are all unfair. It's a mythological concept, this justice business.