Answer
The horizontal rod greatly increases the rotational inertia of the tightrope walker, and stabilizes him against angular acceleration.
Work Step by Step
If the tightrope walker’s CM is not directly over the tightrope, gravity exerts a torque on the person, causing him to rotate (with the feet acting as a pivot). If the tightrope walker is holding a rod, the angular acceleration is smaller, and the person has more time to right himself.
