The Psalm was #89, which begins
Your love, O LORD, for ever will I sing;
from age to age my mouth will proclaim your faithfulness.
For I am persuaded that your love is established for ever;
you have set your faithfulness firmly in the heavens.
But this was followed by another bloody reading from the current cycle in the Book of Judges, one of those parts that make people stop reading the Bible and raise the fair critique, "How can a God described as 'loving' be behind this other stuff?"
For me, the answer is that God's love meets and works with our flawed race wherever we are. Sometimes, God has to work with bloody, primitive people. Sometimes, he has to work with people who think they are the apex of civilization while behaving in ways that would disgust their bloody, primitive ancestors. God's love is "faithful in the heavens," but must infiltrate a world that "prefers darkness to light" and does not receive its own Creator.
"Even a caveman can do it" - even a caveman can feel the wonder of a greater reality, exult in the grace of unexpected good things come his way, interact with the love of God even if he thinks it's emanating from a magic rock. Even a caveman can receive some measure of God's love, because God's love is not contingent upon some attainment of human development. For which I am very thankful, especially on days when reality breaks in on my most comfy ignorance and illusions.