Power can make a person stricter in moral judgment of others while being less strict of their own behavior, new research suggests.
To simulate an experience of power [researchers] assigned roles of high-power, such as prime minister, and low-power positions, such as a civil servant, to participants. The participants were then presented with moral dilemmas. Results showed that compared with low-power individuals, high-power participants judged others more strictly for speeding, dodging taxes and keeping a stolen bike, while finding it more acceptable to engage in these behaviors themselves.
The underlying cause is three-pronged. … Power makes people more egocentric, and so they focus on their own needs; power reduces a person’s ability to take on the perspective of others; and power makes people feel psychologically invisible. “They become unaware that their behavior can be observed by others,” Galinsky said.
More here. So why are we morally hard on the low status, and easy on high status? One obvious answer: to increase our own status, we want excuses to affiliate with the high status, and to avoid affiliating with the low status. Biased moral standards help.