Democrats were crying foul yesterday after a Bush campaign official managed to cross-reference Vietnam and "Seinfeld" in criticizing an ad for John Kerry. "John Kerry's campaign seems to be summed up this way: 'I went to Vietnam, yada yada yada, I want to be President," Bush campaign spokesman Terry Holt told The Washington Post. Holt's swipe came as a put-down to a new ad by the Massachusetts senator touting his war hero status. On the TV sitcom "Seinfeld," "yada yada" was shorthand for information someone would rather gloss over. Kerry spokeswoman Stephanie Cutter immediately demanded an apology, and former Sen....