Economic inequality is bad because it has a profound negative effect on most people's self-esteem and ability to enjoy life. With high inequality, money becomes more valuable and people start to think of everything in terms of money. Even romantic relationships become money-oriented. It's not uncommon for marriages to break up because of financial reasons. Wealth inequality causes more human suffering than moderate p…
I think that your point ("People who lived in communist Russia will often tell you that people were happier under communism") is unsubstantiated. I've heard this a FEW times, but mostly from older (60+) unskilled laborers (like taxi drivers) who are simply unable to adjust to the new world.
Almost all Russians realize that their country is better until capitalism. (If you want to call what they have here 'capitalism', it's more like 'crony capitalism').
Nor do I agree with "It is human nature to want equality". Humans will always jockey for status and power. That is human nature. If it can't be done with money, then they will use whatever other kind of social 'currency' exists to try to rise in the hierarchy of status... just like the pigs in 'Animal Farm'... or communist party leaders in the Soviet Union.
Mostly, people are who complaining about inequality are really complaining that they ended up at the bottom of the hierarchy and have how no clue how to or no willingness to climb it.