I genuinely don't know how to explain that the fact it requires an income of more than 21/hr to meet basic needs is all the justification that should be required.
Maybe if we stopped thinking of employees/contractors as "labor" and thought of them as people it would be easier to empathize with their needs. Do you think that your friends, family, and loved ones deserve a wage that meets their basic needs? Why shouldn't all humans deserve the same?
That's not how capitalism works and that's not why companies exist. Companies pay you what you worth to them. A company is not a human, it doesn't care whether you have a family and are struggling or not.
The primary purpose of a business is to maximize profits for its stakeholders.
Then the answer is simple, if we want humanism in the way we deal with employees, than businesses that seek to maximize profits for their stakeholders should be outlawed.
Which is exactly what we're talking about. Instead of getting paid what we're worth, we have mega corporations like Uber breaking laws, ignoring regulations, and then lobbying for regulations when it suits them. It's rather disgusting.
> Like what makes educated people more valuable as human beings?
On average, educated people contribute more value to the functioning of society. I can drive myself around. I can't perform my own heart surgery.
The argument that all humans are inherently equally valuable is specious reasoning. I can come up with all sorts of trolly car conundrums that if you were forced to choose, you'd make a value judgement about which person to save because they have more value.