I don't think you understand the extent of the distrust and resentment that existed between the French and the Germans. It goes back much further than 1871.

You could probably go back to the Middle Ages, but let's start with Napoleon. His invasion of the German territories officially destroyed the last vestiges of the Holy Roman Empire. This, of course, was neither holy, nor Roman, nor an Empire any longer; but it did symbolize the national identity of the Germans at the time. (You ought to know that German national identity does not hinge on a political nation state but rather on a shared language, culture and history.) Apart from this abuse of national pride, Napoleon's armies of occupation were seen as evil oppressors, and his forced recruiting of soldiers for the Russian expedition didn't help either.

Napoleon's defeat, though a great relief to the rest of Europe, was a blow to the French pride. (As far as I am aware, he is still a national hero in France to this day.) It was followed by the Vienna Congress and the reordering of Europe, after which there was a period of relative stability. However, the distrust remained, especially as Prussia became more and more powerful.

Come 1871, defeat in the Franco-Prussian War was an absolute disaster for France. It was the greatest humiliation imaginable, both militarily and politically. Its armies outclassed, its king captured, it had to watch as the enemy paraded through the streets of its beloved capital. Adding insult to injury, Bismarck proclaimed Wilhelm of Prussia Emperor of the united Germany in the mirror hall of Versailles - the holy of holies of the French monarchy.

France could not forget. In the next four decades, it watched Germany's growing power with growing fear, seeking alliances to protect itself. At the same time in Germany, France continued to be presented as the historical archenemy. (In this period, a huge statue was built depicting an ancient Germanic tribal leader, Hermann. Symbolically, his raised sword points towards France.)

Everywhere in Europe, nationalistic fever ran high. The lead up to the Great War was an incredibly tangled mess of bad diplomacy that ignited animosity rather than allay it. Everybody knew war was coming, and nobody was trying very hard to prevent it. After all, they thought, it would be short, it would be glorious, and there would be the chance to right old wrongs.

When war came, almost everybody rejoiced. The Franco-Prussian war was still very much in living memory, and the military leaders of France and Germany were baying for blood. Four years of the deadliest war ever seen stilled the peoples' thirst for blood, but not the hate. Now it was France's turn to humiliate Germany, which it did it's utmost to accomplish with the Treaty of Versailles. (Signed, of course, in the same hall of mirrors that had seen Germany's triumph in 1871.)

France tried to ensure that Germany would never be able to fight another war. Of course it failed, and of course the attempt only served to increase German hatred. Hitler and his party then played a masterful game of psychology with the German people, in which the "shame of Versailles" had a very prominent part. War broke out again, the French defenses broke, and once again German soldiers paraded through Paris. Not one to forgo symbolism, Hitler had the French government sign their surrender in the same railway wagon that had seen the signing of the Armistice of Compiègne (which hat ended fighting on the Western Front in 1918). I need not go into the brutality of the ensuing occupation of France.

With this long history of mutual hatred, it is an incredible feat of the post war governments of Germany and France that they managed to forge a friendship between their nations. A lot of the credit is due to Charles de Gaulle and the first German chancellor, Konrad Adenauer. Their Elysee Treaty of 1963 paved the way for what has become a very close international friendship and the center piece of the European Union. But it was a long road.