Ask if by rich people they mean funding?

If no: ask them to discuss functions uniquely fulfilled by rich people in the allocation of funding. They will likely need time to reflect, so plan to resume later, but the best answer is expediency/dispatch via unitary agency, and it’s easy to demonstrate why this advantage (A) is outweighed by numerous liabilities via human fallibility and (B) isn’t actually unique.

If yes: they have already conceded, but you might then shift to the question: must there be people who are poor?

That is a meatier conversation, since it challenges their assumption that people require imminent threat of destitution to motivate productivity. You can brute force this argument via strong scientific consensus, but for most you need only rely on their belief in human dignity. Just be aware that the most difficult branches of this conversational pathway are exceptions they might have carved out: groups for whom they hesitate to ascribe human dignity. But the revelation of such bigotry is important for their own personal reflection.

GL