This idea got hijacked by the anti-tax, anti-government, anti-union movement who want to lower workers' salaries.
Let's set unions aside for a minute, because you have a point albeit with many caveats there. There are very few complete anarchists, so I'll set those people aside as red herrings.
People who want lower taxes want to keep more of their paychecks. This means greater nominal salaries ceteris paribus, since net pay is less than gross pay due to taxes.
People who want the government to spend less want to decrease the debt. This means greater real salaries ceteris paribus, since debt expands the money supply and devalues the currency.
Now, you are right to some extent in that less unionization generally means lower nominal salaries for the workers. However, those greater salaries come at the expense of lower employment and labor force participation. We compensate for this with welfare spending. Welfare recipients are not adding value to the economy, in a general sense, and so while they can spend the money they receive, they do not typically build wealth in doing so. This is inflation, and so diminishes the real value of the workers' greater nominal salaries.
There is no doubt that there are plenty of people who want to make a quick buck without doing much to justify it. But they are no less prevalent in government and union management than in business. You have to separate intentions from results.