Ad hominem is the devil’s favorite tool when his lies are rejected.
Ad hominem works about 75% to 90% of the time, depending on whom the target is. But it blows up all at once if the target turns on the abuser and asks, “You talking to me?”
Suddenly the abuser is put in the position of outing himself (or herself) as a boorish, ignorant bully, forced to either rationalize their attack by escalating it, or shrink back intimidated. If the bullying is escalated, that only invites further retaliation, and a most grievous situation emerges, in which all reason is taken away and emotions are in full control.
Watching a cornered rat comes to mind.