Trump’s tariff obsession came up in conversation this morning and I realized that many people may not have seen this great documentary about Trump and trade. If you’re curious about why he is so stuck on it, this explains it: As FRONTLINE and NPR explore in the new documentary Trump’s Trade War, Trump has taken an aggressive stance on trade for decades. He has pushed a tariff strategy since he first toyed with the idea of running for president in the late 1980s — a message that bore notable similarities to the one that helped propel his 2016 campaign. As the film recounts, Trump’s ire was then directed at Japan’s trade practices. “The fact is, you don’t have free trade. We think of it as free trade, but you right now don’t have free trade,” Trump said in a 1987 episode of Larry King Live that’s excerpted in Trump’s Trade War. “A lot of people are tired of watching the other countries ripping off the United States. This is a great country.” He shared similar sentiments in an interview with Oprah. “He believed from the beginning that there’s really nothing worse than being laughed at,” Marc Fisher, author of Trump Revealed, tells FRONTLINE and NPR in the above scene from the documentary. “And he came to see the Japanese as laughing at the United States and taking advantage of the United States by stealing the jobs, by dumping product here.” After the Japanese economy cratered, though, Trump would shift his focus to a rising economic…