In my opinion, bonding a handrail is probably more dangerous than not bonding, especially if the rail is not touching the water.
If a rail is not bonded, then touching the rail is like touching the concrete.
However, if the rail is bonded, there is a strong path through a human who touches the rail while they are in the water.
In the below video, the person only gets shocked when they touch the handrail.
People assume that the rail was probably not bonded, but I suspect that it was bonded and that provided the path for the electricity to flow.
If the rail was not bonded, the person would probably not have been shocked.
Note: The NEC requires bonding and you should always follow all local and national codes.
Also note that Dr. Sanjay Gupta does not really know what he is talking about regarding electricity or this particular incident.
He is speculating on what is happening and why, but he clearly does not know, and he is really not qualified to be presented as an expert in this case.