What is the importance of the "annoying fly" in the book, Discourse on Colonialism?

Césaire uses the image of an “annoying fly” (53) to represent the nagging, recurring idea that non-European peoples are civilized too—if not more so. Césaire suggests that in order to maintain their sense of self-importance and grandeur, European philosophers and intellectuals do their best to swat this fly - this idea - away.