Another right-ish supporter was F.A. Hayek, who had some positive arguments in favor of it as well (whereas Friedman supported it mostly just because he thought it was better than welfare systems).

Hayek's main argument was that a society based on autonomous individuals, rather than collectivist groups, is more likely if everyone is guaranteed at least a minimum safety net, because otherwise people are forced to cling to birth-related groups (ethnic groups, clans, clannish religious groups, etc.) for their safety net. A short snippet: http://www.kmjn.org/snippets/hayek79_minimumincome.html

Elsewhere he discusses it in relation to choice as well: above a subsistence floor, he opposes much government intervention because he thinks markets made up of individuals making free choices can make decisions better. But below that floor, when people are desperate, you have things that are closer to "I'm going to make you an offer you can't refuse" than an economy driven by free choices. It's unclear from my memory if his worry there is primarily an ethical one, or relating to proper functioning of markets, though it could be both.