First off, it is pure New Republic propoganda that linked Emperor Palpatine to the Sith. Darth Vader, the Emperor's most trusted advisor and Supreme Commander of the Imperial Navy did belong to the old sect, however the New Republic and the newly founded "New Jedi Order" is attempting to smear the Emperor by lumping the Emperor with Vader as proof of some conspiracy. Pure bantha poo-doo if you ask me. The Emperor was, and always will be, just a man who was often a victim of Force-Users, not one himself. It is hypothesized that this is why Darth Vader was often seen with the Emperor. That Darth Vader was simply a guard against the old fundamentalist Jedi who sought to restore their power.

There was chaos before the Empire. The Old Republic, unlike what many New Republic revisionists try to ignore, was at war before the Empire. The Old Republic was crubling under corruption, greed, and wanton violence. The Confederacy of Independent Systems was quick to seize the opprontunity to install themselves as a new power in the Galaxy. Chancellor Palpatine was always reported to be massively relunctant on the power that kept being bestowed upon him. He was however not willing to let the Old Republic fall to the corrupt and greedy. It was when the Jedi attacked him in a failed coup de'tat that Palpatine realized that for the Old Republic to continue, that the old system must be reformed. That it must be more centralized and to not let fundamentalists be able to, without provocation, to instill themselves as rulers. The brave Clone Troopers of the Republic attempted to arrest the offending Jedi and through their malice they attacked the Clones, their brothers in arms for years, and cut them down with their ancient weapons. It left no choice for the Emperor to decree a stronger central government.

There was peace in the galaxy under Palpatine, until a group of terrorists asserted themselves and sought to return the galaxy into war again. They were no doubt successors to the Confederacy, who sore after being defeated at Mustafar and Utapau, sought a new way to destroy peace. They allied themselves with the fundamentalist Jedi, ones who sought to take over the Republic to begin with, and led a terror campaign across the galaxy. They destroyed a research station that they deemed the "Death Star." They killed millions of civilians, along with military personal that were on board; including the war hero, Grand Moff Tarkin.

It is through these actions the Rebels true nature was revealed. The Empeire did bring peace, and the Rebels sought to detroy that peace thugh terrorism and military campaigns. The Emperor had to once again, relunctantly, assume more power to wage a successful war against the upstarts. Ultimately it ended with his death over the peaceful planet of Endor. The Rebels, have now assumed command of the Galaxy along with those who started it, the Jedi.

The atrocities of the Empire are well established. From the subjugation of Toprawa, to the Ghorman Massacre, to the destruction of Alderaan, to the enslavement of many species, the Empire was, consistently, a source of social and actual strife throughout its territory.

However, you're asking if these acts could be justified--if they were the "price," as it were, of the Empire's order. The problem with that is that it implies a lack of order prior to the Empire--which was not the case. The Galactic Republic was corrupt, to be certain, but for the average Republican citizen, life was orderly and secure. The crises of the Late Republic era were manufactured by Palpatine and his allies. Whether he himself and/or his allies were Sith (the evidence for which is hit-or-miss) is irrelevant: whether powerful Sith Lords or mere politicians, Palpatine and his cronies brought down a galactic government for the sake of their own power, and reacted to disagreement and dissent with mass murder and repression.

Follow-up:
How has earlier historians' bias and emotional connection to the Intergalactic Wars shaped our view of the Empire as an evil and immoral faction? Have the rebels ever been put on trial for their war crimes against the Trade Federation and Jabba the Hut?

Not only were all of their actions taken for the greater good, the superweapons they built (capable of destroying both planets (the Death Star) and entire systems (the Sun Crusher)) were manufactured solely for use against the impending Yuuzhan Vong extragalactic invasion - one that, in the absence of benevolent Imperial rule and defense, ravaged the galaxy, irrevocably destroyed many planets, and caused trillions of sentients' deaths.

LOL! Someone has gotten hold of that old satire history put out by the Space Onion on Coruscant! Both Vader and the emperor were Sith, admittedly so!

I can't handle this sub sometimes. How dare you barves lump the New Republic (and by extension, the New Jedi Order) in with the Old Jedi Order ?

I've had our beliefs dismissed too many times as "hokey religion". It's bad enough dealing with the fear and distaste for the Jedi in many Outer Rim worlds. Do I have to deal with this nonsense ?

Look, if you want a Reformed Jedi's perspective, I'll give it. We know the Old Order was corrupt. As far as we can tell (limited historical records after Order 66, a religious genocide that your precious Empire clearly ordered, if you'll actually read the first-hand accounts instead of conspiracy theories), none of the leaders were particularly corrupt. The old counsel was fine enough, character-wise. It was the ideology and the political aspect.

The Old Jedi Order was clearly in bed with the Senate. It's fairly clear to me and to the rest of my brothers and sisters. The Ruusan Reformation left the Galactic Senate without any military force. So the Old Jedi Order stepped in to fill that role. It wasn't intentional, I don't think. They clearly attempted to keep the peace as best they could, but despite the multi-special nature of the Old Jedi Order, the requirement that Jedi be trained from birth distanced them from the cultures and gave them a rather humanocentric and ideologically Coruscantan conservative political stance.

Compare this to some of our current practices:

The teachings of the New Order differed from those of the Old in several ways, and were closer to those practiced by the Jedi before the Great Sith War. Jedi were allowed to marry and have families, and each Jedi Master could train multiple apprentices. Jedi were allowed to use conventional weapons and armor besides their lightsabers, and the wearing of the Jedi robes, while popular, was no longer mandatory. For a long time, the Order was also much less centrally controlled, with each Jedi being given much greater personal freedom and responsibility.

The Old Jedi Order went the way of extreme conservatism and asceticism. We've returned to a purer form of the original order, not the bloated, corrupted fundamentalism of the Fall of the Republic.

More importantly, we're open to alternate views of the force. Our founder, Luke Skywalker, has explored a variety of different views of the Force. As he famously said:

The Force may not have a Light or Dark Side—but we do… and we must choose.

Can you imagine that kind of "heresy" from the Old Jedi Order ? They were Holocron literalists who never stepped outside their ivory tower. Can you even imagine them exploring the Aing-Tii tradition? Me neither.

And we're open to new ways of being involved throughout the galaxy that aren't just military interventionism. Luke again:

I don't propose that we place ourselves in seclusion and pass our days meditating on the Force—though that might be the path for some of us. But I do advocate attuning ourselves to the longer view, and reaching out to others who seek to serve the Force.

That's the sort of clarity that the Old Order lost. I'd appreciate if you could stop buying into the manipulative bullshit the Imperial Knights and the Sith Order keep publishing. There's nothing innately wrong with the Jedi Order. Sure, there are barvy Jedi, but they don't define us as a tradition and a movement. We are a new creature.

Is this question really appropriate for this subreddit?