Libertarians cannot understand the public reaction to Davies' comments: it is a simple matter of capitalist economics, they argue, that people have different values in the marketplace. Look at 16-20 year-olds, whose minimum wage is lower than everyone else's. It is lower because they are on average worth less to employers than older workers, who presumably have more marketable skills to offer.
However, the minimum wage debate is not really about economics, for what it illuminates is the facet of capitalism which we are perhaps most uncomfortable with: the deeply crass way in which it values human beings. The gut reaction to Davies' suggestion is that it is morally wrong: a disabled person is not worth less than anybody else. But on the market, people are worth different things. Young people are (see above); most women are if they are looking to have children; older people are if they are close to retirement. And sadly, many disabled people probably are too.
What stories such as this remind us is that the economic system is made up of human beings for the benefit of human beings, yet it often appears to devalue and corrupt the inherent worth of certain people. This belief has been the basis of the Left's challenge to capitalism from Marx onwards, as it attempted to deal with the perceived 'dehumanising' elements of the market system.
Thus, minimum wage legislation is not about economic efficiency but about humanising our economy. It is about saying that while we are happy to accept that the market produces some inequalities, humans are equal in certains ways - across gender and disability, for example - that our economic system is not free to ignore.