You are incorrect. A union isn’t by any definition a leftist organization. However, a union of labor may become leftist or rightest as was the case of the British Luddites who opposed change, seeking to conserve the status quo. But, a union is a neutral creation that is shaped by the results it desires or as is currently the case in our nation, the desired results of leaders following an agenda foreign to much of the labor movement.
Furthermore, a labor union is as collectivist as is the American Association of Manufactures, the Chamber of Commerce or the NRA.
I'm not buying that comparison. Labor unions in the United States have been formed for the purpose of collective bargaining and collective action against the businesses that employ their members. Those characteristics have been memorialized in labor law at state and federal levels. Fortunately, there are right to work states that have given individuals the freedom to work without the interference from a labor union. Absent the iron hand of government to enforce their thuggery, the labor unions don't compete particularly well in the free market.