Did you not follow the story at all? It's a shame so much got taken out on Danny when they were teenagers, but as adults people continued to go out of their way for him and give him the benefit of the doubt against good judgment, and he kept crapping on it. Did you see what made John snap and drown him? John asks when it's going to end and Danny says it's never going to end. He basically said he's going to terrorize them to try to make them all feel what it may be like to be in his shoes.
Any good decision he ever made was ruined not by anyone else, but by it being followed by a dumb decision.