What Is the Proper Role of the Bureaucrat?

The NYTimes has an article discussing the pipeline being proposed to run across Canada and much of the US.  The pipeline opponents believe that a bureaucrat in the State Department was inappropriately helping a lobbyist for the pipeline, who had a political connection to Clinton.  It raises for me the question of what is the proper role of a bureaucrat:

• the neutral arbiter of the rules, enforcing them as best you can, rather like an umpire in a baseball game?
• the advocate for the cause, like the Army Chief of Staff for the army? 
• the helpful postal clerk, who attempts to guide the aged customer with an odd package through his options?
• the social worker, encouraging the client to do the right thing? 
• the FBI agent, enforcing the law? 

Seems to me all of the above are appropriate in context.  

There's also the question of different personalities: some people are effusive and outgoing, others (the better ones I say with total bias) are reserved and taciturn.

It's often difficult to judge a bureaucrat's behavior fairly without seeing a lot of their interactions with clients/customers.