... but also remember that LBJ, and others of his generation, had been around when Chamberlain gave in to Hitler's demands at Munich in 1938, which then led to World War II and the deaths of over sixty million people across most of Europe and Asia. People of Johnson's generation were traumatized by the horror of such unimaginable devastation and learned a lesson -- never ever show weakness to an aggressor. It's fair to argue that this "lesson" was misunderstood and misapplied to many situations, including Vietnam. It's also fair to argue that the question as to which country was the "aggressor" in any particular dispute was open to interpretation and America was certainly not always benign in its intent. Nevertheless, in the context of the Cold War, all the presidents from Truman through to Reagan took the "lesson" to heart and believed that it was important for the US to always demonstrate strength and resolve in foreign policy. It's also true that for the most part, the American people expected it of their presidents. It's not a surprise that President Obama echoes that sentiment as well.
Furthermore, setting aside the actual definitions of "murder" and "mass murderer", I will take your comment to mean that Johnson was responsible for many people being killed. True. However, the same can be said of many presidents, virtually every one from the beginning of the 20th Century to now. Every so often, every president issues an order that results in the deaths of people. How many Americans died under Lincoln's watch? FDR is beloved by many people, but he was the Commander-in-Chief who oversaw the American firebombing of Japan and is just as much a "mass murderer" as Johnson. Of course, FDR's war was thought to be a "good war" by most people, so no one seems to worry too much about what the United States (and its allies) did to win it. I raise this merely to point out that the difficult moral and ethical questions raised by the use of war are beyond just LBJ (or Obama) and can be applied to many presidents in American history.
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