Indifference is the opposite of Love, and Unitarian Univeralists try to Stand on the Side of Love.
"Standing on the Side of Love" is a slogan that distills for this time the social theology summarized in the UUA' s Seven Principles statement, especially the commitment to the worth and dignity of each person, the right to free search for meaning, the promotion of the democratic process, justice, equity, compassion.
Those Seven Principles do not arise out of thin air. They are the late 20th century interpretations of our 19th century and 20th century theological propositions: the rights of a free conscience, universal salvation, humanist pragmatism.
And those particular Unitarian and Universalist theological suppositions are derived directly from the distinctive beliefs of Enlightenment liberal Christianity, especially the human likeness to God and the human capacity for good. All of which are rooted in the doctrines and disputes that go back to the earliest days of the Christian church, emerging as it did out of the Jewish religious and ethical disputes surrounding the Jewish rebellion of the first century.
And of course, the commitment to love as the opposite of indifference can also be traced through many other religious and philosophical traditions.
None of this is whimsical, or faddish, or novel. Just because we don't often think about the history of our ideas, doesn't mean they are original to us, or that they have no history.