Making the poor poorer...

According to Gary S Becker and Richard A Posner in the Wall Street Journal:

Some economists deny that a minimum wage reduces employment, though most disagree. And because most increases in the minimum wage have been slight, their effects are difficult to disentangle from other factors that affect employment. But a 40% increase would be too large to have no employment effect; about a tenth of the work force makes less than $7.25 an hour. Even defenders of minimum-wage laws must believe that beyond some point a higher minimum would cause unemployment. Otherwise why don't they propose $10, or $15, or an even higher figure?

They title their editorial "How to Make the Poor Poorer". Unfortunately, too true. Why is it that those who propose policies in the name of the poor ultimately do quite the opposite?