Believe it or not, the brain plays a huge role in how we feel about inequality. The frontal cortex can detect "rewards" and it creates a positive feeling.
And people, rich and poor are wired in their brain to have a dislike for inequality.
For example; in one experiment, there was two individuals. One was given $50 and the other was not.
When a poor person received money, their brain became "happy", but had little to no reaction when the money was given away.
Then a rich person received money, their brain had little to no reaction but when the money was given away, it became "happy". the reason for this is that it may reduce the guilt of seeing others start of with nothing receive something
Even though this is the case, both brains would have became less "happy" if someone had received money under unfair circumstances, contrary to how they think they feel.