Answer: His response to the violence he has constantly been subjected to.
Step-by-step explanation:
Throughout the story, Richard suffers physical and mental abuse from his family, white people, the Communist Party. The violence he´s subjected to by his family and society, in general, ends up taking over him, making him feel that he needs to show power through violent acts to earn respect.
In that sense, him burning down the house might be a symbol of the violence within the black community, and the violence inflicted on all of them by white people.