I think it's something that I learned in high school, so it really isn't such an obscure fact. More importantly, it is quite relevant today because the definitions of Left and Right during the French Revolution have their counterparts now.
During the French Revolution, the middle classes waged a class war against the landed aristocracy and the Royals/Nobility. By definition, any political movement that subverts established social order and hierarchy is Leftist, while those that defend it are Rightist. The French Revolution was by definition a Leftist movement, even though it was waged by people from different backgrounds than those who waged Communist revolutions in the 20th century. Different content, same form.
It is a leftist trick used to try to absolve themselves of the their political affinity to the two great evils of the 20th century, communism and fascism, by claiming 20th century European fascism is akin to conservatism in today's America.
It isn't a trick, it's just using the definitions of Right Wing as defenders of traditional property rights and institutions vs. Left Wing as destroyers of those traditional property rights and institutions. By this dictionary definition, of course Francisco Franco was on the political Right, and of course his Republican (as they were called) opponents were the Left Wing in 1930s Spain - Franco defended private property rights, the Left wanted to nationalize private property along Soviet lines. The fact that Francisco Franco didn't seem to have much in common with Barry Goldwater is irrelevant, the American Left is quite different from revolutionary movements in Latin America, Africa, or southeast Asia too.
Unless, of course, you are yourself a communist ...