MIB=Free will. To be able to have free will you must have the choice to do evil. Jacob has touched the losties, he has interfered with their lives and some point. MIB wants to leave the island, yet Jacob is the one keeping him trapped on the island. Therefore MIB does not have free will. Pehaps if MIB leaves the island the world will finally be free. They will have decesions to do evil. Jacob said if MIB leaves evil would enter the world. But people would be free to make or not make these decesions. In the new timeline they have free will.