Drugs are a central theme in "Sonny's Blues," impacting both the users and those who love them. Heroin destroys lives, families, and artistic talent. On the other hand, it also offers a momentary escape from the characters' depressing and oppressive physical environments and serves as a coping mechanism to help them deal with the human suffering that surrounds them. While Baldwin doesn't judge the characters who use drugs, he does present drug addiction as horrible, gut-wrenching, and ultimately destructive.
There is no justification for Sonny's drug addiction, no matter how hard his life is.
Although we don't condone Sonny's drug use, he does a good job of explaining why he turned to drugs in the first place.