No, we can’t assume that a driver of a hybrid is going to run down someone in front of him/her, but the fact remains that pedestrians are hit by cars daily and many of these incidents are the result of driver inattention. Just as a driver needs to drive defensively, a pedestrian needs to walk defensively when crossing a street.
But, when a vehicle is silent (or at least unusually quiet), it is that much harder for a pedestrian to guard against being hit by a car driven by an inattentive driver. And, if the pedestrian is blind, major problems could result.