Earlier quoted context omitted.
I would take a look at this argument done by Obama's main economist. He basically argues that UBI isn't actually that good because it doesn't shrink the gap as much as current systems (progressive taxes and the like). Plus it is a good read anyways because it is a much longer detailed analysis. https://www.whitehouse.gov/sites/default/files/page/files/20...
This seems to make the mistake, I believe, of focusing on "inequality" as a problem. Inequality is not a problem. Poverty is. If everyone has everything they need and most things they want, but a few super rich people own entire planets, I fail to see how that's not a utopian future.
Imagine a farmer working his entire life on his farm. Now that he is reaching the end of his lifespan he wants his children to benefit from his work. He built the house and everything himself.
Why should the government take a chunk out of that? One might argue that the children do not work and therefore this "unearned" income is unfair because it's not possible to choose whether you are born into a wealthy family.
However it is both earned by the work of the father and already taxed by the government through his income.
By the time the father dies the children are likely already 40 to 50 years old but they benefited from his little wealth while he was still alive. The inheritance tax does not affect this. It only discourages using the inheritance efficiently over multiple generations.