Abuse of power is rarely merely a "perception." Put anyone on a pedestal and they begin to think they deserve to be. Certain professions attract those who are power-hungry more than others. Doctors fit the bill. Not all, but certainly some.
Those certain professions that are more power-hungry than others, are more likely to be bankers, politicians, CEOs, captains of industry, TV preachers ... these are the professions that attract the highest number of psychopathic personalities and those with the least social and individual conscience, not to mention being more consumed by personal greed in general. These are the professions that are lionized by the media and fawned over by large segments of the population.
Doctors on the other hand, while being susceptible to abuse of their position just like anyone else can be, do at least have a more altruistic foundation for their choice of profession - they have chosen to help alleviate direct individual suffering and disease. Those in the medical profession who tend to gravitate toward the less personal form of medicine - teaching, research and pharmacology for instance - may perhaps do so for any number of reasons (prestige, income, lack of people skills) but they will not be in personal contact with individual patients.
I think that one of the main reasons many people, in the US at least, have such a bad image of the medical profession, is because it is highly driven by the profit motive. Medical treatments cost exorbitantly more than in other industrialized countries and can be the cause of such unheard of things as medical bankruptcy. If you are in fear of losing all your possessions because of necessary treatments, or worse, not getting necessary treatment because of insufficient means, well, no wonder a doctor can become a scary person to deal with in your personal perception. He will then literally be holding the power of life or death.
Add to that, that a physician is one of few professions by which people can be asked and expected to comply with undressing and nudity. So no wonder many people are uncomfortable and uneasy, especially those who are shy about their body and nudity to begin with. And unease and apprehension does of course color people's perceptions for the worse.
And then let's not forget the wonderfully informative role some of the media can play when real abuses are uncovered. It is shouted from the rooftops and rehashed again and again because of the prurient content. It's that wonderful media combination of sex and abuse of power that is bound to get everyone atwitter.