I think this could be applied regarding their parents in the sense that some of their parents teachings and/or actions did have a negative effect on both Fluttersh and Discord. To elaborate, Fluttershy's parents told her that anger and hate were wrong, but Fluttershy took these values too far, while Discord's parents effected in Discord in being unable to tell the difference between playfulness and maliciousness.
This is not to say that their parent's were completely at fault for their children's actions, but they did have an effect in how they viewed the world.
PS: Anyone can correct me if I got any facts wrong.