Yes
They did not pay slaves, thus the reason to call them slaves
minuimun wage
to get wage increases for their members.
Nowadays slavery takes the form of people trafficking, especially woman and children, to work as sex slaves or to be exploited in sweat shops/factories working for a minimum wage or for no wage. The reason is for greed and money
never
Communism or slavery.
Most likely many black men had no or very little wages after slavery was abolished. The highest wage was likely only several cents per day.
Wage slavery refers to a situation where a person is dependent for a livelihood on the wages earned, especially if the dependency is total and immediate. The person is working but not making enough money to live so they need to work other jobs to make ends meet. The person can't quit the job because they need it to live. This is wage slavery.
professional bodies and trade unions
The original unions were formed because of the extremely harsh work conditions in America at the time. These Unions stood for more worker rights, child labor laws, and minimum wage.
Slavery is not a big thing in the 2014. Slavery was a big thing in the past.
Abraham Lincoln thought the difference was only that wage labor was temporary and slavery was permanent.