There is a photo from the 1950s that shows segregationists holding a sign that says "race mixing is communism." Obviously this isn't what communism is, but conservative right-wingers have a habit of doing this. What is the history of right-wingers equating communism with "anything they don't like"?

The "communism is anything I don't like" message of conservatives goes way back judging from this photo from the 1950s. What is the history of people equating communism with "anything I don't like"? Why do conservatives continue to do this despite easy access to sources indicating what communism really is?

My next question concerns the actual photo itself. Why would American segregationists automatically equate communism with "race mixing" when pretty much every communist state I can think of was relatively ethnically homogeneous? Didn't communist officials in places like Russia promote the separate, but parallel development of ethnic minorities in their own republics and autonomous regions?