George Santayana once said, "Those who cannot remember the past are doomed to repeat it." That is why History is so important, to make sure that we remember the past, and thus avoid repeating past mistakes, and repeat successes. This applies even to ideas.
The Idea that the USA should not be "the World's policeman" didn't start with Ron Paul. It dates back as far as 1812, and is connected to a much broader policy of "Isolationism." However, when we look at the history of Isolationism, we see that it didn't work. The USA, due to its power, has great responsibilities. Derelicting these responsibilities only led to greater and more destructive conflicts demanding US intervention later.
Another Idea, that we should react swiftly and early to problems of even the slightest interest has also been tried. History tells us that when the US intervened early, we usually avoided larger more destructive conflicts down the road.
These two ideas now are being put to the test over Syria, as to whether we should or should not intervene. Will our intervention be another case where we prevent a bigger situation later, or will it be one of the exceptions (like Vietnam). Knowing the past can help us avoid mistakes in the past being repeated, just as Santayana said.
The only disadvantage to knowing the history of any idea might be that "Ignorance is Bliss" but that cliche is not as powerful as George Santayana's quote.