It’s an age-old and tiresome story, and I’ve watched more than one friend undergo some variation on it. He’s got what you want: the knowledge, the erudition, the passing grade on exams, the dissertation signature. He’s brilliant, an acknowledged expert in your particular area of study, an incisive thinker and an wide-ranging scholar, and he provides quick, detailed (some might say terrible and swift) feedback on the many difficult but instructive assignments he requires. In short, just the kind of professor from whom one might, in theory, secure a first-class education.
He’s also, not to put too fine a point on it, a jerk.