Problem is hindsight is 20/20. With the mindset we had then about not allowing communism to spread- and events that had taken place in Vietnam during and after their revolution, added to agreements made following WWII there was a good case for the Vietnam War. On the other hand- given the strong probability that Johnson created a situation and then over-reacted to it is hard to say it was reasonable for the U.S. to get fully involved when it did- if ever. Then we have the issue of the dims being really good at bringing about crisis and war and not being able to deal with the reality when it happens- there are just to many ifs ands and maybes. If Johnson hadn’t micro-managed- if so many things. It is good to analyze history, but hard to see all of the sides of the equation of things in the past.
It is the Butterfly Effect - we will never know. It is a good exercise to help people realize that actions have consequences. Obama is the result of the Perfect Storm of the 60s.