Radio Raheem and his boombox are a very symbolic and powerful character in Spike Lees Do the Right Thing. Raheem shows that the minorities are all internally angry and enraged that they are considered less and looked down upon for their color. Radio Raheem does this by walking around with his boombox blasting the song Fight the power. Furthermore every time that he ever is in a point of tension with his boombox aside form the moment with Sal he simple slowly raises the volume on the boombox in till the other people are drowned out with the sound of Fight the Power. By doing this he is showing that one day the minorities will raise and be equal and then be greater. As Mookie said to Pino about having the black community raise up its "inevitable" . 

However on the other side on the spectrum Sal was just the summation of the feelings of most racist people of that time. He was all business when it came to dealing with the color people in his community allowing them to spend money and work for him without an issue but when it came time for them to take a stance that is where the line was drawn . Sal states in the beginning of the film that he is going to kill somebody today but i think that was just a to prove how angered he was internally about how he is uncomfortable with the community he works in and how all he was there to do was sell pizza not make friends or help the community just to work and go home. however this attitude had terrible repercussions because this feeling of rage and discomfort that Sal had reached its peak when Radio Raheem and Buggin' Out started a peaceful protest because he no longer was just selling pizza he was forced to either speak as an equal to the people of the community or just explode. Sadly Sal choose to exploded and it resulted in the burning of his pizzeria and death on the block.