Spiritual reason? It is like asking why there is evil in the world. That would be the right question because it will cover all possible such cruelest deeds now as well as the past. Otherwise we will only jump from one incidence to another.
Well evil exists because of the evolutionary nature of creation. Evolution from one species to another is not a complete cut off. The new species even as it leaps carries something of the previous species. Thus the human carries in himself the beast and the snake. Slowly through a process of evolution the beast gets tamed and humanised while the serpent changes into a little worm. This happens through long spaces of time. To give an example, it is just few centuries ago that the gladiators or even in wrestling one could kill the opponent. So also instant justice, looting wealth and women was part of sections of humanity. But now generally we like to follow the rule of law in most parts due to the coming of rational order. Yet sections of humanity have yet to evolve to this stage. So too there are people who are like beasts and the Rakshasa in their consciousness even though they have a human body.
It is therefore, from a spiritual perspective, a problem of incomplete human evolution. The spiritual solution therefore is to hasten the collective evolution of mankind through a deeper integral education and a progressive spiritualisation of the race. Until then the Rakshasa has to be dealt with the only way he understands, that is to the strong arm of the law. It is a progressive spiritual evolution that will eventually give us the permanent solution we are all looking for.
Affectionately,
Alok Da