Do the kingdoms of the world compare themselves to tiny seeds and bits of yeast? Not at all! To provide marketing and communications for a worldly kingdom is to traffic in hyperbole, comparing the earthly realm to whatever is biggest, most powerful, influential, and affluent. This is done in order to evoke fear, respect, obedience, and conformity. It is a world where lies, exaggeration, and violence are the commerce around without which the realm could not exist.
Jesus, however, compares the kingdom of God to a tiny mustard seed and bits of yeast - small, fragile, vulnerable things that, if cultivated, will produce great things. Jesus seeks to evoke something entirely different from the message of the world about its kingdoms. The kingdom of God is one that nurtures, nourishes, shelters, and invites all to seek refuge and food. In using these images of nature, Jesus also reminds us that God's kingdom is in fact God's. It is not of human origin or control.
If religious institutions traffic in images of power and engage in lies, it is a sure bet their kingdom is one Jesus rejected in a desert long ago. The kingdom of heaven and the church are not synonymous terms. The church is called to be the kingdom of heaven and model its values, and when it fails to do so the kingdom of heaven is still here, for it dwells within each one of us called to live its values.