STORIES ABOUT spat-upon Vietnam veterans are like mercury: Smash one and six more appear. It's hard to say where they come from. For a book I wrote in 1998 I looked back to the time when the spit was supposedly flying, the late 1960s and early 1970s. I found nothing. No news reports or even claims that someone was being spat on. What I did find is that around 1980, scores of Vietnam-generation men were saying they were greeted by spitters when they came home from Vietnam. There is an element of urban legend in the stories in that their...