ARBALA, Iraq, May 7 — American soldiers battled insurgents led by a rebel Shiite cleric on Friday, killing scores of Iraqis, as the cleric delivered a defiant, derisive sermon that dismissed President Bush's expressions of regret for the abuse of Iraqi prisoners. "What kind of peace could come from you or your agents when you feel pleasure at torturing prisoners?" the 31-year-old cleric, Moktada al-Sadr, said to cheering supporters at his mosque in Kufa. "How are you going to control the world when you can't control...