According to 'War and Peace', German’s self-assurance is worst of all.

Pfuel was one of those hopelessly and immutably #self-confident men, self-confident to the point of martyrdom as only Germans are, because only #Germans are self-confident on the basis of an abstract notion— #science, that is, the supposed knowledge of absolute #truth. A #Frenchman is self-assured because he regards himself personally, both in mind and body, as irresistibly attractive to men and women. An #Englishman is self-assured, as being a citizen of the best-organized state in the world, and therefore as an Englishman always knows what he should do and knows that all he does as an Englishman is undoubtedly correct. An #Italian is self-assured because he is excitable and easily forgets himself and other people. A #Russian is self-assured just because he knows nothing and does not want to know anything, since he does not believe that anything can be known. The German’s self-assurance is worst of all, stronger and more repulsive than any other, because he imagines that he knows the truth—science—which he himself has invented but which is for him the absolute truth.

Even though I know the truth, I'm not sure that one can generalize like that.