Researchers proved that a person has over 60,000 thoughts per day. All such thoughts contain positive and negative aspects.
If those negative aspects dominate positive thoughts in human beings, it will lead to distress at individual level. This distress will cause disharmony at world and society level.
Such thoughts at individual level create damage to him/her and also to the society and the world as well.
So it is quite important to overcome such negative thoughts and cultivate peaceful thinking as discusses in the above point.