Worker's Unions are controversial because they can force the rich to give up some of their money. That means the owners will spend vast sums of money to eliminate the threat. Back in the day, on financier said that he could hire half the working class to kill the other half. It should be noted that most of the workers' rights that are common today came from Unions. The 40 hour work week, safety regulations, restrictions on child labor, equal pay for women, unemployment insurance, social security, and other things we take for granted were won with blood and struggle.