Every generation of pure-bloods from ancient and noble houses are brought up the same way. The father grooms his son into the perfect heir and teaches them how to earn respect and power. The boy grows up and, liking where he was in life, teaches his child the same techniques to slither their way to the top of the food chain. This is how most slytherins are made.
This was all messed up by Sirius Black. He had been raised the same as any other heir, but he did not take to the lessons very well. His first public display of acting out was at and annual ball hosted by the Malfoys.
A house elf had made a small mistake and had been cruelly punished. Sirius had yelled at the Malfoys. That had gotten him a beating at home. Things only got worse when he was sorted into Gryffindor, but we all know that story.
Unknown to anyone, this caused the start of something much bigger than just the story of a disowned wizard. These actions were much too late to affect Sirius's generation, but they turned out to significantly impact on the next one.