The House on Un-American Activities was a direct outgrowth of The Cold War. Its purpose was to "finger out" Communists in America--and went after many "High Profile" people--especially in the Entertainment Industry.
Unfortunately, its M.O. was very similar to the Salem Witch Trials--if someone accused you--you were then Guilty until proved Innocent. MANY cooperated with the Committee--just to be prevented from being named themselves.
And yes, the Chairperson was Joe McCarthy of Wisconsin.
Who said "We Have Nothing to Fear--But Fear Itself"?
"I say YOU'RE the CUTEST one. No, I say YOU'RE the CUTEST One. And we go on like that from dawn to three."