Innocent Communist deals drugs to optometrists!

It is almost impossible for a character like Billy Pilgrim to exist nowadays. A person as innocent and harmless is bound to be affected by peer pressure and bullying early on in life, and I'm betting he'd turn out a smoker or crackhead. It just seems so much more likely that he would be almost forced into bad situations, unless he learns to fend for himself and be more social. The Billy we see in Slaughterhouse Five is always pushed around, even as an adult, and is not capable of asserting himself or giving an opinion about any matter (other than time travel after his trip to Tralfamadore). 

Adolf Hitler, a source of inspiration for all. 

The world is not a place for people who are too happy-go-lucky and always expect things to work themselves out. Billy would be traumatized by almost being drowned by his own father. This would probably translate to a lack of trust towards his own father, and that could extend towards the family. Child Billy tends to not get too close to his peers at school, preferring to keep to himself. His marks aren't too great, and his self-esteem is constantly taking hits from other kids calling him a loner and from his parents (probably his dad) looking down upon him. 

Teenage Billy then discovers a whole new realm of possibilities with drugs, which he is introduced to in high school by other kids who feel like him. They are among the first that Billy can relate to, so he feels the need to please them. His innocence is pulled away from him with every puff and injection, and it only get worse. Those he thought were his "friends" now charge him and abuse him, making him feel even worse. The result? More drugs! Life continues downhill, with our poor Billy, who already left home, dropping out of school. He can no longer find any change for crack and starts to look a lot like this. 

It's unfortunate, but most guys like Billy don't conveniently meet an optometrist with an unloved, marriage-seeking daughter and the ability to give them a high-paying and respectable job in return for marrying her. Then again, most guys like Billy don't keep that same attitude past high school, since it is so unrealistic to live a life like that.