Madonna really likes to beat a dead horse, doesn't she? The singer dissed her (much younger) rival Lady Gaga onstage again, this time in Atlantic City. Madge dedicated her performance of her Golden Globe-winning song 'Masterpiece' to Gaga, and she added a nasty insult to the "dedication." Doesn't she have anything better to do than take cheap pot shots at Gaga? This rivalry is so January 2012, isn't it?