, 10:15 AM
The Sith aren't "evil" -- they're merely desperate.
Remember, the Republic is a large, corrupt and oppressive expansionist empire and the galaxy's worst criminal regime. The very existence of the Sith Order is a result of that corruption.
From the earliest days, the Republic and Jedi have emulated history's worst criminals.
When the Dark Jedi and Light Jedi had an ideological disagreement on the role of emotion in the force, the Light Jedi response was a war -- followed up with executions. The remaining Dark Jedi who didn't take up arms were stripped of their possessions and citizenship and expelled into deep space -- reminiscent of Hitler's treatment of early German Jews.
As the Sith Empire of old formed and grew, it eventually bumped up against the Republic, and the two went to war (as is common). When the Sith were defeated, the Jedi and Republic response was mass genocide of all Sith and Imperial citizens. Hundreds of billions of men, women and children -- mostly civilians -- were murdered in the most grotesque ways imaginable. Jedi lightsabers and Republic blasters shot babies in their cradles. Republic ships delivered death to Imperial cities from above.
Ziost, Korriban and hundreds of other Sith worlds were murdered.
The Republic also destroyed almost all of the Sith cultural artifacts on Korriban, in an echo of the Taliban's own destruction of ancient Buddhist artifacts in Afghanistan.
The current Sith Empire is a remnant survivor of those two unspeakable crimes, committed by a Republic and Jedi Order whose "values" are most definitely at odds with their actions. Its call to strength and power is a demand for survival in a hostile galaxy, while its rage and hatred as powerful emotional elements are understandable in a group of people who call for passion to fuel actions. A group of people subjected to genocide by an evil Republic and its fundamentalist nut-job religious Jedi council aren't going to be feeling love, romance or self-sacrifice after seeing most of their friends, families, and homes destroyed repeatedly.
In short, any "bad" emotions fueling the Sith are a justifiable result of Republic and Jedi crimes against the galaxy.
Clearly, Sith cannot exist within the evil Republic. Within the oppressive order of the Republic/Jedi, religious freedom is banned and unpopular speech results in prison time. Thus, the only choice is war and eventual hope of victory.
The Republic and Jedi's evil is of a more toxic and corrosive nature than that of some Sith psychopaths like Vitiate (who, incidentally, would have probably been destroyed long before the new Sith Empire arose if not for the Jedi/Republic genocide of Imperials). It's a totalitarian empire behind the smiley, happy-face rhetoric of "peace."
The apologia by the Republic's adherents is amusing.
"What about Alderaan?" What about Ziost, Korriban and hundreds of other Sith worlds? Alderaan was destroyed by a Republic-designed weapon, so is largely an echo of the countless other worlds the Republic brutalized and murdered.
"What about Palpatine's attack and deception?" Palpatine's destruction of the Jedi order and Republic was a legitimate act of self-defense by the Sith, who had been brutally hunted down and exterminated -- simply for their beliefs -- over the millennia.
Where the Jedi and Republic have shown depraved cruelty -- the mass murder of all Sith and Imperials after military victory -- the Sith have shown restraint. The Jedi and Republic bombed Korriban into cinders at the end of the first Sith War. The Empire, upon seizing Coruscant, simply held it in order to get a treaty granting the Empire respite from Republic oppression -- yet destroying Coruscant entirely would have been appropriate as a response to the callous destruction of Korriban. (Ironically, the Sith's ethics would get them in trouble later, as Corsucant would be a valuable resource towards helping the Republic later in the war.)
Are the Sith "good guys?" No. They're trying to survive against a massive colossus of a Republic, headed by religious extremists called "Jedi," seeking to exterminate them and deny them existence as free and sovereign beings... all while arguing that their cause is "right" because it's written in their holy books.
Hundreds of billions of victims of Jedi genocide will tell you the truth, if you care to look long enough or listen to the whispers in ruins of long-dead cities.