Yes, that is true. It is not power that corrupts people. Power and money only unveils the true self of a being. When on a good position and in power and authority, a person will have the capability to do what his heart desires. The corrupt will desire corruption. They will abuse their authority, strength and power. You must have come across bullies in life, they are the miscreants who abuse the little physical strength that they possess. Some people may pretend to be all nice and decent, but as soon as they get a chance, they will stab you in the back. It is all a matter of chance. The moment that reveals their true colors. Such people will appear to change when their circumstances change, but in fact it is only now that their inner selves come into the limelight.
On the other hand, there are people who when acquire power and authority, will try to use it for the betterment of mankind. They will always be givers. It is not true to say that power corrupts, because power is the test of a being's character. We are who we are, our circumstances do not change us. We already possess the capacity of either treating people good or bad. With the gain or loss of authority or power, we only either gain or lose the capability to treat others the way we want to. The bad natured, disrespectful and shallow human beings may pretend to be nice to you, when you are better off than they are, and as soon as they gain power over you, they will get back to being their normal shallow selves. While the good natured and respectful people will always remain who they are, no matter where and at what position or status they are.