Germany had won the return of Alsace-Lorraine in the France-Prussian War but still built a large army aimed at France.
What did France do to earn that hatred from the Germans?
Berlin was afraid that France might start a war to get the lost provinces back.
Thus, Bismarck tried to keep France isolated in Europe. He knew that France would need a partner or two to fulfill this ambition. Bismarck knew that Germany could deal with any single aggressor - but as a team they would have the advantage.
Napoleon, for starters. France was what Germany later became - the top dog in Europe. France's offenses weren't as great as Germany's would be, but they must have done their share of pushing around. Also, I'm not sure how much the Germans hated France. Maybe it was more like the Germans wanted to rule Europe and the French were in the way. There was certainly much envy, given that Britain and France had gotten first and second pick of colonies in Africa, Asia, and the Pacific, and Germany and the other European countries had to argue over scraps.
In addition, France was aligned with Russia, which presented a major threat to Germany's eastern frontier. Instead of seeking peace, the German General Staff contrived the Schlieffen Plan and an army to carry it out. The plan called for a rapid and powerful march through Belgium into France and the capture of Paris for a quick victory. The plan failed, just barely.
Napoleon. And Napoleon III.