In South Africa, during the era of apartheid, white labor unions urged that a minimum wage law be applied to all races, to keep black workers from taking jobs away from white unionized workers by working for less than the union pay scale.
Some supporters of the first federal minimum wage law in the United States -- the Davis-Bacon Act of 1931 -- used exactly the same rationale, citing the fact that Southern construction companies, using non-union black workers, were able to come north and under-bid construction companies using unionized white labor.
These supporters of minimum wage laws understood long ago something that today's supporters of such laws seem not to have bothered to think through. People whose wages are raised by law do not necessarily benefit, because they are often less likely to be hired at the imposed minimum wage rate.
Labor unions have been supporters of minimum wage laws in countries around the world, since these laws price non-union workers out of jobs, leaving more jobs for union members.
People who are content to advocate policies that sound good, whether for political reasons or just to feel good about themselves, often do not bother to think through the consequences beforehand, or to check the results afterwards.
If they thought things through, how could they have imagined that having large numbers of idle teenage boys hanging out on the streets together would be good for any community -- especially in places where most of these youngsters were raised by single mothers, another unintended consequence, in this case, of well-meaning welfare policies?