I have heard this from way too many people. Many of whom I felt were rational adults. There are issues that will need to be addressed regarding the use of electric bicycles in certain locations and on certain public thoroughfares, however the idea of cheating is ludicrous, and this is why.
We are not in competition with any other mode of transportation. Electric bicycles are not competing with cars, therefore cars are not cheating by getting somewhere faster. Motorcycles are not cheating by getting anywhere faster than a bicyclist. Bicyclists are not cheating by getting somewhere more efficiently than a pedestrian. So why do we say those commuting on an electric bicycle are cheating? It is clear that the stigma of a bicycle as only a toy or a tool of sport has completely altered our collective thought DNA. Prior to the influx of the automobile bicycles were used by all who could afford one, and horses moved the rest of polite society. Cars came roaring down the alley and in short order the bicycle was no longer in fashion. At that time the idea of a simpler easier life was to be admired and chased after. As a society we have seen the folly of those old ways. Every other day a new article comes out about the dangers of being sedentary on our health, and how fat we have become, and what these conditions are doing to our longevity and health. Today the enlightened among us have discovered that sitting on a chair at home, getting into a chair with a car around it and driving to a chair in our office is making us sick. If you have an electric bicycle that you use for commuting you know the value of the motor, and you also know that you still pedal and enjoy getting your respiration up, and when you want to push it cut the power and get to work, the extra weight of the electric bicycle makes for a serious cardio workout.
Commuters on electric bicycles are not cheaters, not even close. This is a new segment that is only now being explored by those of us brave enough to live deliberately and challenge the status quo.