Do you mean that there is no fact of the matter as to whether an act in a context is moral? Because if that is your claim, I disagree.
$40k * 300M = $1.2 * 10^13, or the whole GDP of the US
Okay maybe that's too luxurious for the common people. Let's say only 20k per year, and to only 200M people.
$20k * 200M = $4 * 10^12, or about the total federal spending for 2015.
So how exactly is the 'richest' nation in the world able to afford this, easily?
Also, this would presumably replace Social Security and other welfare costs (or retirees would be excluded).
And finally, people would still be working. I'm sure the taxes I pay would more than cover the cost for giving it to me.
I wonder if the argument against it is something like this: imagine for every person, they have some amount they are willing to contribute to said scheme. However, unless the total amount needed to fund such a project is small, if you don't force everyone to contribute then the cost will be significantly higher per person. Then, because it's higher than what some people want to pay, they choose not to pay although they would have otherwise. After that happens, the price increases more, and this effect continues.
But the question to ask is: does that justify the use of coercion to secure funding? I.e., does efficiency justify the use of force?
Morality is relative, but I don't understand your views on it. If a society is rich enough to give a good life to all their members, is it immoral to do it?
What about keeping a big part of the population afraid of how are they going to pay the rent tomorrow so you have cheap and available workers? is that moral? specially when we live in the richest societies of history?
People that believe in the overwhelmed goodness of markets should investigate a little more history. For instance: the ten hours bill in the UK (https://en.wikipedia.org/wiki/Factories_Act_1847) and how the "laissez faire" crow of the time opposed to "restrict the working hours of women and young persons (13-18) in textile mills to 10 hours per day" because its immorality.