The world

Why does the world have to be so cruel, why can't everyone just get along?

I guess people have been asking this same question for years upon end now and I've come to a conclusion to think that perhaps it may be greed for some and jealousy for others, but I believe that one day a man betrayed his beloved friend and then so did the remaining part of the world. Betraying people has became human nature to most of the world, and then when they feel guilty for destroying somebody so innocent and pure, they the start to blame the victim for being different. Why can't this world have some common sense?