WASHINGTON, May 4 — A group of Vietnam veterans tried to pick apart Senator John Kerry's war-hero biography on Tuesday, questioning a combat wound and denouncing his antiwar activities as a betrayal that should disqualify him to be commander in chief. The group cited a document from a doctor who said that in December 1968 he treated the wound for which Mr. Kerry received the first of his three Purple Hearts and that it probably resulted from an accident, not hostile fire. "Some of his crew confided that they did not receive any fire from shore, but that Kerry had...