Who controls a panel by policing the time that a person takes to give an opening statement, politely cutting off or redirecting rambling answers to a single question, and ensuring that all have equal opportunity to express their views?

A moderator is responsible for controlling a panel.

Explanation:

The moderator of an event controls the pace of the event and ensures panelists responds to questions in an orderly and controlled manner. He allocates time to panelist and ensures they respond within the stipulated time. He also has a responsibility to the audience to make sure the conversation is meaningful to them.