First, because the non-human person can get no affirmation. Husbands and wives could not love one another simply because society denied the humanity of the wives. Nor could they truly love their own children for they hadn't truly been loved themselves. And children saw role models not of love, but of slavery and abuse. Love is an active principle.
Love requires then three elements.
Miss one of these elements and you don't have love. This is the reassurance we all need that it's okay to be here, in this time and place. Words don't count. Only actions which are in themselves life-affirming. This is the main topic this morning.