Well, this is figurative language, or ought to be. Someone knowingly behaving badly, making unhealthy choices, is “digging his own grave.” This figure has been nicely turned in recent years by writers concerned with overeating: they say gluttonous eaters are “digging their own grave with a spoon.”
But the way this student uses the phrase, the figurative language loses its poetic dimension and offers only a bizarre picture to us: Sonny is busy out back digging his own grave, and Dad doesn’t want to watch.
I’ve written frequently about the case of the ex-pro football-playing father killed his son to save him from the miseries of drug addiction. Students grappling with this case do tend to get lost in verbal tangles. Figurative language offers itself up on the sacrificial gridiron and is scorched beyond recognition. This example is just one of many.
Here, my student was right: the father believed his son, who had quit high school varsity sports and spent most of this time lying in his room listening to music and smoking marijuana or drinking “cheap wine,” was dooming himself to a slow and horrible death in some skid-row crack house. The son refused all offers of help with his “problem,” and of course Dad believed that the end was inevitable. Sonny was digging his own grave with his drop-out tune-out behavior. But my student’s earnest desire to emphasize this parental fear and filial self-destruction literalizes the sentence. Suddenly, Sonny is in the backyard digging his grave, and Dad is standing by the kitchen window, occasionally peeking out and then pulling the curtains closed again, not wanting to watch the digging. Clearly not wanting to watch. As a parent, and all.
Note that he does not want to watch. The sentence, though, makes no suggestion that Dad is trying to stop his son from doing all that digging. “Go on and dig,” he may have said to his son; “just don’t expect me to watch!”