Paul is the main character of the book. This book illustrates his story and him, as the narrator. This dialogue applies to the patriotic teacher, Kantorek, who has no experience in military, and diverts students to choose war.
However, this excerpt illustrates Pual's feeling of how men, with no or little power, can bring in unhappiness into the world (here, by enrolling themselves into war). For instance, Kantorek is just a teacher and is not at a very high post to influence individuals. But, he keeps persuading kids to join war. Which, in return, brings a lot of misery to their lives as well as to the whole world.