The business community in the 1920s was able to use the Red Scare to help get the general public to side with it over the labor movement. It was able to do this by painting the labor movement as a communist and radical movement.
In the years right after World War I, there was a great deal of fear of communism in the United States. The Soviet Union had just come into existence as a country through a communist revolution. There were many immigrants from Europe who held communist or anarchist beliefs. The US seemed to be moving towards radicalism. This could be seen, in the eyes of some people, in the Boston Police Strike and the Seattle General Strike of 1919.
Since people were worried about communism, it made sense for the business sector to say that unions were run by communists. This would turn public opinion against the unions. Once this happened, both government and the public would be more likely to support employers against unions. This would work to the business sector’s advantage because it would weaken the unions and allow the businesses to make fewer concessions to their workers in regard to things like pay and working conditions.