Two things to remember:

1) I don't think anyone is saying that inequality, as a general principle, needs to be extinguished from the earth (as if such a thing were possible). Rather, it's the degree of inequality that is troubling.

2) When we talk about equality, there is a major difference between equality of opportunity and equality of outcome. Many people are fighting for the former, not the latter.

Equality doesn't have to mean everybody is exactly the same. It can also "simply" mean that when you argue that 1+1=2, it holds the exact same weight as when someone who is prettier or richer does. That is not a hindrance to progress, that is progress, and enables progress in turn.

The alternative is not being able to say that 1+1=2, or that Earth moves around the sun, or that mass surveillance and blowing up kids with drones are terrorism and not fighting terrorism, when some interests more powerful than you would rather not have you say it. We've been there, we are there, it sucked, it sucks. The costs of too much inequality outweigh the benefits; at least if you're concerned with intellectual honesty and human dignity over bling. If you just see that "these pyramids couldn't have built without slaves, and pyramids are so super shiny and useful!" your mileage might vary. But I don't see it that way.

And although I don't even see why evolution has to be the ultimate value (i.e. we have no proof that achieving star faring civilization is somehow "better" than ameoba swimming around in water, we just have our bias in the matter)... extreme inequality would mean one entitity exploiting and controlling all others: no more competition, and therefore no more evolution. So I guess the desirabe state is somewhere between everything and everyone being exactly the same, and one subset owning everything and forcing it into paralysis to fortify its own position of power.

Inequality of opportunity is bad and what we should focus on. Difference in income between high and low earners is irrelevant as long as the folks at the bottom can be comfortable and can pursue happiness in their own way. Being envious of wealth is bad.

If high income earners can freeze out low income then it's very bad.

> Why do all think that inequality is bad?

Because if you define "bad" as "produces human misery", inequality, in and of itself, has been shown to be bad. Relative deprivation has been demostrated to be a major source of disutility.

> the way to evolution

Right. Which is why your society throws any deformed children of a cliff and you send them when they are five to live amongst the wolves for several years after which those that return become warriors.

It's nice to have someone from Ancient Sparta writing on these forums.

On a more serious note inequality has some very negative sides for those benefiting from it as well. Humans aren't totally emotionless creatures, that react to others suffering with cold disdain.

Evolution is pretty much a brute-force solution to a really hard problem (survival over a ever-changing environment), while we humans should be capable to come up with different strategies and optimizations to solve problems, which means that we may just able to get more benefits from a equal and fair society ultimately.

Thank god we are all equal in death. That's the only justice left in this world.