You've taken everything out of context. Sith motives are not only driven by passion but by anger, hatred and lust for power. They're passionate about dominance, control and destruction of the Jedi.
Being passionate about music, film or writing or other creative processes is different to being passionate about chaos and destruction.
Considering how many people have one night stands and can remain emotionally detached in this day and age I'd say that's fairly normal.
To add to the Sith principles: They teach through pain, suffering and emotional beatings. Surely being in a constant state of hatred and rage doesn't promote rational choices?