Why is arthur ross a blacklisted screen writer?

Arthur Ross was blacklisted as a screenwriter during the McCarthy era due to his alleged connections to communist organizations and leftist political beliefs. In the 1950s, the House Un-American Activities Committee (HUAC) targeted individuals in the entertainment industry, and Ross's refusal to testify against others in Hollywood led to his being blacklisted. This effectively ended his career in mainstream film and television for many years.