Why does Kerry now oppose the American presence in Vietnam?

John Kerry, a Vietnam War veteran, opposed the American presence in Vietnam primarily due to the devastating impact of the war on both American soldiers and Vietnamese civilians. He became increasingly disillusioned with the war's justification, highlighting issues such as moral contradictions, the loss of life, and the lack of a clear purpose. His experiences in Vietnam and subsequent activism fueled his belief that the U.S. was causing more harm than good, leading him to advocate for withdrawal and a reevaluation of American foreign policy.