Answer and Explanation:
Americans started associating union members with extremists or extremism, when, for certain reasons, the U.S. federal government mounted attacks on the personal rights of union leaders, people, foreigners and organizations in 1919 and 1920, thus influencing most Americans to associate union members with extremists/extremism.
The fear that Americans had for labor unions stemmed from the growth of local organized labor union movements during the first World War—World War I: The labor unions went on a number of strikes during the war, and many workers were ready to sacrifice their jobs and suffocate government activities in order to improve their own working conditions. President Woodrow Wilson had always supported labor unions/organized labor. However, his support waned and actually ended when unions started organizing strikes and temporarily closing the industries that helped to strengthen the nation's efforts on war.
President Wilson, government officials, and many American citizens felt that labor unions and their members (workers) should have valued the nation’s interest much more than their pockets or private interest. The president told labor unions and workers not to strike, and that after the war, they could demand for better wages and working conditions. The union and workers halted strikes and waited. However, after the war ended in 1918, the union and workers began to strike in large numbers: In 1919, two million workers went on strike and put the nation in turmoil.
The strikes, which had never taken place to such an extent prior to the time, came as a shock to many Americans who thought the country had been good enough to allow foreigners and people to run free businesses. In fact, many Americans didn’t see the need to have labor unions that would suffocate the nation. As a result of the strikes and unrest over working conditions, bombs were exploded at the homes of a senator in Georgia, and the Attorney General at the time—A. Mitchell Palmer; when many other violent acts were taking place, the police in Boston also went on strike.
All the violent events that resulted from the strikes were too much for Americans to handle, and so they started launching campaigns against unions whom they suspected of being extremists. In response to some of the violence, many Americans in various cities carried out violent attacks against unions, groups and people whom they started calling extremists. These incidences lead Americans to start associating union members with extremists.