Man needs to belong. Man needs a family. Man has a need for companionship, community, cooperation and camaraderie. Man has a need to bond and stay connected, we need relationships. We are happier when we are in a good relationship. We are healthier when we are in a good relationship.
Humans deteriorate when we do not communicate, we fall apart when we are not united, we easily get sick when we are not in a prosperous relationship. Unity helps build the path to self-realization. Unity helps build trust.
The inability to connect causes narcissism, it causes loneliness, it may even cause suicide. Unity demands love. Unity needs respect, the respect for each individual human rights. As humans we may not be equal in all respects but we must all have equal rights to opportunities prosperity and happiness.
Most of all humanity needs unity with God.