If a candidate tells you: 'I left company x, b/c my manager was a dickhead, and that I'd rather work somewhere for good people, then compromise my dignity and integrity just to make a manager look good', means that guy actually has a backbone. A weak person will bend and please his manager, even though what the manager is demanding might be damaging to the company on the long run (you see this often in tech. companies).
Fair, but I wouldn't advise anyone, under any circumstances, to badmouth an ex-boss at any stage of the job search process. It's one of the most common interview fuckups.