Final answer:
Sacco was questioned about his political beliefs because they contributed to the public's negative perception of him, influenced by the Red Scare and nativism of the 1920's. His and Vanzetti's affiliation with anarchism made them suspects in the crime and highlighted the prejudice immigrants faced at the time.
Step-by-step explanation:
The prosecution likely questioned Sacco on his political beliefs because they were an influential factor in shaping public opinion against him. This was a period where nativism and fear of radical ideologies were prevalent, particularly the Red Scare, which saw a widespread fear of communist influence in America. Sacco and Vanzetti's connections with anarchist movements, their support for violent tactics, and their association with individuals on the Department of Justice's most-wanted list, would fuel the belief that they were not just guilty of the robbery but also potential threats to national security.
Additionally, the trials took place during a time of heightened anxieties regarding immigration. Italian immigrants and other minorities faced discrimination, and their political and social beliefs were often viewed with suspicion. The details of Sacco and Vanzetti's trial and execution demonstrate the intersection of criminal justice with issues of ethnicity, political belief, and immigrants' rights in the 1920s.
It is clear that the cultural climate and nativist sentiments of the 1920s played a critical role in both the trial and the subsequent conviction of Sacco and Vanzetti. Instead of being judged solely on the evidence related to the robbery, their political affiliations and ethnic background were also put on trial, affecting the fairness and outcome of their case.