Final answer:
The U.S. soldiers' actions in Vietnam, which included war crimes, contrasted sharply with the values of freedom and democracy and included severe violations of war laws. President Diem's government contributed to unrest through corrupt and repressive policies. Such actions threatened the moral authority of the United States in the eyes of both its citizens and the international community.
Step-by-step explanation:
The involvement of the United States in Vietnam, particularly the actions of U.S. soldiers, stands in stark contrast to the principles of freedom and democracy the country was purportedly fighting to promote. According to John Kerry's testimony on April 23, 1971, U.S. military personnel engaged in war crimes which included ra-pe, mutilation, and the indiscriminate killing of civilians, as well as other acts of unwarranted violence and destruction. These actions constitute war crimes as they are severe violations of the laws and customs of war, which are designed to protect civilians and prisoners of war, and to restrict the types of violence and destruction that can be wrought during armed conflicts.
Additionally, the government of President Diem was responsible for intensifying unrest within Vietnam due to its corrupt and repressive policies, which discriminated against the country's Buddhist majority and suppressed political opposition with brutality, leading to increased civil disorder and contributing to the justification for increased American involvement in the conflict.