For that first know Code of the Sith
Peace is a lie. There is only Passion.
Through Passion I gain Strength.
Through Strength I gain Power.
Through Power I gain Victory.
Through Victory my chains are Broken.
The Force shall free me.
Their code is more about personal freedom and power. They don't want to work with rules set by others and want full freedom to do whatever they feel doing. That's why they transformed Galactic Republic into Galactic Empire, so that they can do whatever they want.
There is debate if Code of the Sith is canon now or not but it's safe to assume it is. Because the line
Through victory, my chains are broken.
did appeared in Star Wars: The Clone Wars s04e21.