Thinkers begin with assumptions about human nature, and then proceed to rationalize behaviors and suggest improvements to order and efficiency based on those assumptions. I'm no different.
When it comes to my assumptions about human nature, I believe that power corrupts. Or at least, power leads to an increased tendency to take up the added opportunities and benefits associated with it. Where there's suddenly the opportunity to exploit, why wouldn't people take it up? We can't rely solely on the goodwill of human beings to do good and avoid being corrupt. I don't blame the powerful from taking advantage of their power. Why shouldn't they? In fact, considering one's payoffs (or capacity to get away with something) seems more predictive of one's behavior. It is naive to hope that those in power know the "right" thing to do. Even more so when the morality of our actions is a subjective matter, open to interpretation and debate.
The corollary to this assumption is that rather than devote time and effort to encourage those in power to behave, it is the masses who should be empowered. Power is a social construct and thus doesn't exist in a vacuum - it is nothing without the endorsement of followers and subservients. Thus, instead, I would hold responsibility of power abuse-prevention to the empowerment of followers, both potential and existing. Teach them to think for themselves and ask just one more question. Remove their ignorance. When the masses are critical, leaders cannot take advantage of their ignorance. That is a safer bet to the prevention of abuse of power than educating leaders on how they should behave and hoping that they will.