He was eulogized by Christians, Jews, Zoroastrians and Muslims who denied His claim. His teachings are universal and the standard for human action. They are not merely theoretical and intended to remain in books. They are the principles of action. Results follow action.
Mere theory is fruitless.
When practical activity has been manifested, the teachings of God have borne fruit. They become united among themselves, then unite others. It is impossible to unite unless united. This proves there were dissensions and lack of unity among His followers. Hence His admonition to unity of action.