The thing is you are reading Sith culture as though this Sith Empire is made up of a bunch of fallen jedi or regular people who learned Sith teachings. The SW is a member of the Sith Race. Whether that means they are a Sith Pureblood or a Zabrak. They are Sith. They are decendants of the many survivors of the Great Hyperspace War and the purge that followed. Its true that Dark Side teachings are the primary focus that the Sith value. Its to be expected that Hatred and Anger, which are both carnal emotions, are the emotions that are easiest to tap into. But it takes a true master of Sith teachings to tap into Love and other positive emotions. Using these emotions a Sith can become an even greater beacon of light than a Jedi. Walking hand in hand with the Force. Neither dominating the Force nor letting the Force dominate them. But Light Side teachings hamper and cause issues as well. The desire to show hesitancy and not include themselves earlier in the Mandalorian conflict, even though the Madnolorians were slaughtering and conquering planets and threatened the Galactic stability, thus leading to people like Revan and Malik, who were not masters, to rebel in order to fulfill the age old promise of the Jedi. To uphold and protect the Republic. A LS-SW accepts that there are faults. It accepts that there is a way to improve the Empire. Youy even have the choices to become a follower of the teachings of Revan, knowing that the Light and Dark mingle to closely to truly ever be separated. They can even work to restore the LS teachings via the Holocron in the Dark Temple.

The big thing for my LS-SW, is he's a man of Justice. Right or wrong have everything to do with what he does. He has a strong code of honor, but isn't above being underhanded if it means he accomplishes his goals. To summerize, he's flexible. He believes in Freedom and seeking power and knowledge wherever it can be found. He sees the wisdom in the jedi's teaching, but believes that their denial of passions is weak and does not prepare Force users for the power that emotions can give. Not only that, but he's a true believer in the philosophy of Revan. DS Jaesa does not appeal to him. He's more likely to have her sucked out of the airlock than allow her to run rampant like a Star Wars version of Frakenstein's Monster.

I'm kind of surprised Bioware hasn't stepped in here and given an answer about their reasoning yet.

Consider me signing on for this. I find it frustrating that SW is the only class you have to be a certain alignment to "qualify" for a relationship. -signed.