Possibly triggering

You've been warned

Sam and John would fight a lot throughout Sam and Dean's childhood but Dean was always their to stop or defuse them.

Of course Sam was too young to do the same for Dean.

John wouldn't always hit Dean. If he did it was completely by accident.

He only got violent when Dean really messed up. Or when Sam left for a while.

The reason Dean complies with John almost always is because he doesnt want a fight. And when Sam and John fight he tries to defuse it as quickly as possible because he knows Sam makes John angry and when John gets really angry occasionally a hand will raise.

Dean does everything he can to protect Sammy because "Dang it Dean I said protect your brother for once!"  

Dean has no purpose in life except to protect Sammy. That's all hes been told to really do except hunt.  So if he gets hurt because Sam fought with John then so be it. Because he loses his main purpose without Samuel.

The reason Sam gets so angry with Dean isn't completely because he obeys to John too much, it's because Dean only really obeys John because of Sammy.