HR: Which side to take - Management or officers

Of late I am thinking...which side should an HR Personnel be? This is based on my discussion with one of the my senior HR colleague on related issues. Most of the time I interact with senior management people, much higher in terms of seniority and authority and I deal with the issue related to officers (read- general employees/ non unionized category).
Sometime we tend to take side of management (intentionally or unintentionally) and ignore the cause of common officers just to make our task easier. But what happens then? We loose out our face in front of the employees for whom there is no union to fight for. Really...Isn't this our duty to put forward their concerns in front of management and get them resolved ? Management may feel bad about that, but we shouldn't be concerned about that...after all we are the 'people champion' (refer 4 pillars of Dave Ulrich). The very foundation of HR stands on the faith and hope of those officers who are not able to put up their case to higher management.
Currently I am in a manufacturing firm known for it's liberal HR policies. If I feel this here, I wonder what about the service sector (esp IT sector) where there is no history of union and labor laws...There the role of HR is even more critical....
I am still thinking...but surely, I will always see...Customer first (read- officers)