I know this was posted a long time ago, but I'm also studying La Haine this year, and I agree with the idea of it being about pride. I think it shows the idea that sometimes you have to swallow your pride and reject your false ideals in order to make change and to survive, both for Vinz and Grunwalski.
I also think that it's strongly connected to each of the characters' views on death. Vinz sees killing a policeman as a path to revenge and respect, Hubert sees casualties as unnecessary and to be avoided at all costs; but the old man laughs and makes a joke of his friend's death. It seems to show the insignificance of death and the way that it is a part of life that people have to accept and deal with. It highlights that idea of the insignificance of death and its inability to change the system in any way, an argument that Hubert arguably uses to dissuade Vinz from killing the Skinhead later in the film. It also foreshadows the death(s) at the end of the film, and what little difference that will make to the system.