Sin is that serious. Like a cancer it destroys all that it touches. It must be dealt with and must be removed. Which Jesus paid the price for with His death on the cross. Before His death, he taught just how serious it was, and that is was to be avoided, and dealt with. He also taught how serious it is to lead others toward sin. Finally he taught about the reality of hell, and all who refuse to have their sin dealt with will face the punishment of Hell.