I didn't write out my homily today and I won't be able to reproduce it verbatim, but here's a summary/approximation of what I said. The Gospel is a good one, and I touch on it, but mostly I was digging into this line from the Psalm: "Love the Lord, all you His faithful ones!" (Ps 31:24).
Then, against this worldly view, I gave the classic definition of St. Thomas Aquinas (I don't think I mentioned him by name), that love is the choice to prefer the other's good to one's own. I stuck with the example of the love between a husband and a wife, and talked about how a good husband chooses his wife's good, even when he doesn't necessarily feel like it. I mentioned material good, in working hard to support the family, and in taking care of his wife when she's sick. I mentioned spiritual good, in working not to be a source of temptation to sin for her, and in praying for her, and so forth.
Then I added that love always has a sacrificial character to it. In choosing to love my wife faithfully, I am making the choice not to love in that way any other woman. It's a giving up of something that might feel good, for a much greater good. (It ran through my mind as I was saying this, that the celibacy of the priesthood is another good example of the same kind of sacrifice; but that didn't make it off my tongue.) I may have given another little example here, but I don't recall exactly what I said.
Then I dug even deeper into this character of fidelity and sacrifice, and talked about love as the image of God's love. God's love, being perfect and infinite, spills over into creation, even to creating each of us as a unique, individual person. The most complete form of human love, that between a husband and wife, spills over in the same way, in creating new life; this is a clear sign of the great mystery of love, that can't be reduced only to emotion. Another sign of how human love is an image of God's love is the creation of beauty in art, architecture, and music, that we use liturgically to show and make real our love for God. It's not mere adornment, but an objective quality of what we make to show our love for God. (Beauty itself can't be reduced to an emotional response in an observer, but is objective, etc.)
Even more than creativity of life and beauty, divine love is reflected in human love in its radical freedom. God is utterly free, being perfect and infinite. We too are free, to choose to love, or to choose not to love. In the Gospel (from the Sermon on the Mount), Jesus is teaching us how to choose, how to use our freedom for the best end. When we pray, and fast, and give alms in a godly way, we give the best witness to the freedom, the creativity, the sacrifice and fidelity, of love for God and neighbor. I concluded with a short exhortation to follow this teaching, to choose to love our spouses and our children with that kind of faithful love; to love our friends, co-workers, and neighbors; and above all, above all, to love God with faithful obedience to His Word. I think my last sentence was, "The world cannot drown out this faithful witness, no matter how loudly it proclaims its lies; and the Word of God will not be silent, no matter how quietly we live it in this life."