LONDON — Exclusions and a red card. In other words, just another wild women’s water polo match between the United States and Italy. This one was in the Olympic quarterfinals and the U.S. women’s water polo team kept its unbeaten string intact with an emphatic 9-6 win against Italy, a long-time nemesis. Melissa Seidemann had a hat trick and Brenda Villa and Kelly Rulon each scored twice on Sunday night at the Water Polo Arena in Olympic Park. The United States had trailed 2-0 in the opening quarter. Italy’s Coach Fabio Conti was red-carded and sent off in the fourth quarter.