Final answer:
The detail that best supports the idea of the US government overstepping civil liberties is the criticism from civil rights advocates about the blurring of lines between terrorism and lawful protest.
Step-by-step explanation:
The detail from the text that best supports the contention that laws and actions such as the USA PATRIOT Act may have been used to overstep civil liberties is "prompted charges from civil rights advocates that the government had improperly blurred the line between terrorism and acts of civil disobedience and lawful protest." (Paragraph 4).
This statement points directly to the criticism that federal government powers, as expanded by the Patriot Act, have potentially been applied in a manner that confounds legitimate dissent with terrorism, thereby infringing upon the protected rights to free speech and protest.