What does it Mean to be Un-American

here is a union organizing song from the 1930's called
Which Side Are You On? [1] It says that when it comes to values and rights there are no neutral positions. The question needs to be answered by each of us in our time on our own issues - What are your values? Which side are you on?
At the same time, beware of "sides" and partisanship - they can lead to discord and dysfunction.
I recently heard a progressive commentator say that a new government initiative was Un-American. He was speaking about the ban of transgender people from the military. It could just as well have been a conservative saying the Affordable Care Act was Un-American creeping socialism or an Alt-Right KKK leader saying that racial equality is Un-American. We have a president who thinks regulations that stop coal mine owners from dumping their waste into rivers and streams is Un-American. Growing up I learned of the House Un-American Activities Committee (HUAC) and its post-WW II hunt for Reds, and I was taught that the committee itself was thoroughly Un-American.