This verse compares “tying a stone in a sling” to “giving honor to a fool.” Slings were long-range weapons in the Old Testament world – ancient artillery.
So a soldier or shepherd who tied a stone into the pocket of his sling would make it virtually useless as a long-range weapon – even a waste of valuable resources if he threw it. In fact, it would be just plain stupid!
Honoring a fool is compared to such an act of stupidity. It only empowers and emboldens the fool in his folly. Honoring a guy (or gal) like that can even cause them (or others) think that such behavior actually pays off.
While the ancients would snicker at the thought of a shepherd or soldier tying a stone into his sling, they might still struggle – like the rest of us – with giving honor to a fool. It is an especially difficult decision when the fool is a family member or good friend.
But “honoring a fool” produces nothing of value for them or anyone else. An exercise in stupidity and futility, it’s as useless as tying a stone in a sling and hoping it will be an effective long-range weapon!