I disagree with his assumption that our role is to do the manager's job. Clearly it is impossible to effectively manage staff from a central department. Unfortunately many managers, either through a lack of ability or a desire to avoid unpopularity, are willing to sidestep difficult decisions, for example on discipline or redundancy, and make personnel officers take responsibility. My role is to advise managers on good practice.
Effective managers require less personnel advice than incompetent ones. Companies with effective managers tend to perform well. Saying personnel managers cause poor performance is like saying firemen cause fires.