Final answer:
Americans fought back against HUAC through legal challenges and protests, thereby challenging its actions and advocating for the protection of civil liberties.
Step-by-step explanation:
Americans fought back against the House Committee on Un-American Activities (HUAC) through legal challenges and protests. These methods were used to challenge the constitutionality of HUAC's actions and to advocate for the protection of civil liberties. Organizations like the National Civil Liberties Bureau (which later became the American Civil Liberties Union) were formed to challenge the government's policies against dissent and conscientious objection. By utilizing legal means and public demonstrations, Americans sought to resist the repression and intimidation tactics of HUAC.