Several points need to be made here.
First point... Michigan did not ban or prohibit labor unions. You are still absolutely free to join a union in Michigan, if you want to. The new law allows you the freedom to make the choice. Personal liberty.
Second point... The term "labor movement" is an inaccurate misnomer. Unionized labor represents 11.6% of the labor force in America. The other 88.4% is non-union. Therefore, "labor" is represented by the overwhelming majority of non-union laborers. It is the "unionized labor" movement, and these people need to be corrected every time they refer to themselves as the "labor movement" because it's not accurate or true.
Third point... The entire "median income in RTW states" argument should be tossed. Most of these states were largely blue states until recently, and many of them just recently became RTW states. Change takes time, it doesn't happen in a year or two, and we can't look at a chart of statistics and make any sort of rational determination about this. That said, you can look at any one of the top examples the "unionists" present, and you will find the rate of growth in median income far exceeds their non-RTW counterparts. These states are booming with new business and jobs, whereas, cities like Detroit are deteriorating before our very eyes.
Fourth point... Statist Marxist Democrat government is only 'friends' to the unions because they are a source of money and power. The Democrats are the Party of Government, and will throw any union under the bus to further their agenda and protect their power. We see this today with the coal and oil industry, unionized industries that are being literally destroyed by the Democrats, in order to appease another power demographic, the environmentalists. In Poland, it was the labor union who rose up and overthrew the totalitarian government.