A society should search to maximize utility. Let's make some numbers up. One starving person has a utility of 1. One not starving person has a utility of 10. One mega-ultra-rich person has a utility of 100. One ultra-rich person has a utility of 99.
If you take money from 1 mega-ultra-rich person and give it to 2 starving persons:
99-100 = -1
2*(10-1) = 18
+___
+17
So the society gains 17 units of utility from the change. Are you claiming that 1 unit of utility for the rich is more valuable than 18 units of utility for the poor? Because the rich person agreed to society's contract, and figured out that they gain much more utility from roads, labor, police, laws than they lost from UBI. A rich American wouldn't be rich if they didn't receive any benefits from society.