Also, even if you give everyone a basic living with for example, basic income, income inequality is still a problem, because to get a bit more of what you want you have to sell more of what you do. This unavoidable causes tension, because labor , value and price can get distorted.
But not also that, because if you were to see that income inequality is a problem on how the value is captured, not created, this means that people with skills and capacity to create a lot of value are not getting rewarded for it, which is detrimental for all the members of society, except those that get the direct benefit of the value capture.
Well that too, but the tension comes directly from the inequality. e.g. Being hungry sucks, but it sucks more if you see fellow citizens live like kings.