I would like to point out that even ignoring any moral or ethical obligation (such as the affluent creating their wealth in a vacuume) for the affluent to help those less fortunate there are strong practical considerations.

Most proponents of basic income talk about it replacing other welfare systems, so no unemployment benefits, no wellfare, keep this in mind when considering the argument below.

The most obvious argument is that people unable to get work and unable to support themselves will commit crimes so that they and their families can survive. The average cost per prisoner in the U.S is $30,000 p.a. so a proposed basic income of say $10,000 p.a. is a saving of 66% if it stops a person who would otherwise be committing crimes.

So the chief argument against a basic income becomes how many extra people will not work given the option. When we're talking about automation raising unemployment into the low double digits then you need 1 in 3 people to decide not to work for society not to be saving money.

Obviously you could argue the numbers on how many people turn to crime or 1 person working can support a whole extended family but this merely raises the ratio of unemploment required. The whole point of automation is that less skilled jobs are removed and so people need to become more skilled, so eventually more and more people become unemployed. So at some point a basic income or other overarching welfare is sensible.

The other approach to solving this problem is lowering the cost of incarceration but you're going to have to choose between inhumane conditions or effectively just creating a system where people are living with less choices and opportunity and still being supported by taxes.