All I really need to know about Donald Trump I learned from “Ghostbusters II.” An undercurrent of hate and fear-a river of slime, if you will-is fueling his march toward the Republican nomination. How far this takes him depends on whether, as Ray the Ghostbuster put it, we can summon what is best about America before it’s too late.For those of you who live full, productive lives and have yet to see the sequel to Ghostbusters-the goofball scientists who rid New York of ghosts-let me catch you up. In the movie, a river of slime flows under New York, turning everyone it touches angry and violent.