over what does the big fight start in the shower room? why does MAC get involved and why does the cheif get involved?

In the shower room that afternoon, the men who went on the fishing trip are ordered to take a special shower to ensure they are not carrying parasites. George refuses to accept an enema, and protests loudly. McMurphy intervenes on his behalf, and gets into a fight with Washington, one of the black boys. Warren, one of the other black boys, pins McMurphy’s arms from behind, but Bromden pulls him off and throws him into the shower. Another black boy grabs Bromden from behind, and Bromden runs backward and smashes him against the shower tiles.