According to John Kerry, how did many U. S. soldiers treat Vietnamese civilians?

They mistreated, tortured and abused them.

Explanation:

John Kerry testified before the Senate in 1971. He accused the Vietnam veterans of committing horrendous crimes during their service in the Vietnam war. He stated that the American soldiers repeatedly abused innocent Vietnamese women, cut off ears, limbs and heads and randomly shoot many peasants. They raged villages and wiped out the entire communities, poisoned their water and killed their livestock. There were cases of abuse, torture, kidnapping, setting fires, taking prisoners or intended murder.

Kerry's testimony was dismissed at first but later confirmed by research on this subject.