The House Un-American Activities Committee and then later the Joe McCarthy Government Oversight Committee in the Senate were classic cases of guilt by association. Because they assumed some Americans were Un-American and not deserving of being Americans simply because of people they may have associated with and political positions they may have held. Not because of any illegal activities they have been involved in. Which is how we are supposed to judge people’s involvement in criminal activity.
The United States a liberal democracy where Americans have the right to believe what they believe. And say what they want to say with a few exceptions. Like encouraging violence or libeling people without any basis in fact. Yelling fire in tight public spaces. But for the most part our own politics is our own business. And we are free to either express our own political opinions, or opinions about any other subjects or not. And not be held criminally libel because of what we believe.
But what we got instead from these Congressional communist investigative committees was guilt by association that ruined a lot of good productive Americans lives. And for what, so people on the far-right and people simply just looking for political advancement, Senator Joe McCarthy comes to mind, could have a big issue and use it to advance their own political careers. No matter who they may hurt along the way which is about as Un-American as it gets.