The Elder Scrolls

Yes

Whereas i disagree with the Stormcloaks, I still don't believe in the Empire's ideologies either. The Stormcloaks have the right ambitions, driving a failing empire out of their homeland to regain their freedom of religion. And if Hammerfell could separate while having an infamously unsteady government can successfully rebel and successfully fend off the Thalmor, why can't Skyrim? And yes I disagree with the Stormcloak's racism and Ulfric's principles. He's a xenophobic narcissistic asshole. Again, I dislike the Stormcloak's racism (for the most part, argonians are tree-simping bastards,) but it makes sense given Tamriel's geography and how each race is separated into its own country/province. Racism is inevitable with worldbuilding like that.

Onto the Empire, they also have correct motives. the Empire has always been a mostly great government. Reman Cyrodiil's time was the best Tamriel had ever seen, and bringing that back would be great. But that's not realistic. The Empire is failing, and has been since even before the Oblivion Crisis. Rebellions were starting before it happened, and the Oblivion Crisis was the catalyst for the Empire's fall. Things only descended from there, with the rise of the Thalmor, the rise of false emperors, etc. But the Great War was the definite point at which the Empire was beyond salvaging. Losing Talos, Hammerfell separating, the fall of the Tribunal and the Red Year, Black Marsh having always been an uninhabitable land of bastards, everything is pointing towards the Empire's fall. 

So the Empire is trying to bring back times from thousands of years ago and falling apart. The Stormcloaks will be xenophobic and horrifyingly unsteady for at least a decade after Skyrim's establishment as an independent country. The rise of the Thalmor is inevitable, and it's impossible to tell how the future will pan out. 

And when you call the Nine Divines the 'Eight' that's also invalid. Talos is valid, as is Wulfharth, Penilal Whitestrake, and Zurin Arctus. Though only one on that list is recognized as a god, all of them are Shezarrines. Shezarr is also known as Shor, Sep, Lorkhaj, and, most well known of the different aspects, Lorkhan. Lorkhan is technically a Divine, though he was killed by the rest of the Divines for his betrayal in manipulating the Gods into creating Mundus. Returning to the prior topic, Talos/Tiber Septim was a Shezarrine, an aspect of Lorkhan, Lorkhan reincarnated in a mortal form. So when Tiber Septim died (or didn't, he apparently achieved CHIM in one of his apparently many lifetimes, it's complicated and I love MK,) he became one with Lorkhan again. Talos is Lorkhan, and therefore a valid God. 

So why would the Thalmor ban worship of Talos, and therefore Lorkhan? It goes back to the creation of Mundus. I'm sure everyone knows that Aedra means "our ancestors" and Daedra means "not our ancestors" in Aldmeris. That's because when Lorkhan manipulated the Gods (or let them consentually, the stories varies on who you ask,) into creating Mundus, it was contreversial to all of the Gods, of which there were many. The Nine Divines sacrificed their power to create Mundus, while the other Gods (the daedra and the magna ge,), either didn't contribute at all or only sacrificed some of their power. Thus, the Nine Divines (and other gods, I'm about to explain,) lived on Nirn. I don't know what happened and why the Nine still exist, but the Gods living on Nirn had their power wane over time, and eventually became the elves and men. So the Aedra are the ancestors of mortals, whereas the Daedra didn't create any races of Nirn, and therefore don't have any relation to them. 

With that out of the way, the depictions of Lorkhan varies by race. The elves consider him to be the Devil of their pantheon because in their eyes he manipulated the Aedra into sacrificing their power. If the Aedra hadn't done that, the elves would still be gods, and not mortals. In the humans' eyes, Lorkhan is responsible for their creation, so they worship him as a proper god. That disagreement in religion has caused innumerable conflict between the races. 

That still doesn't explain why the Thalmor would completely ban Talos worship. Why would they destroy the human's freedom to worship over a single disagreement in an extremely similar religion to their own? The dunmer literally worship demons by other elven standards, and the other elves haven't done much to stop them. 

Well, the way gods work in Aurbus is that the more worship they have, the more power they have. It's a partial reason as to why Daedra worship is so taboo, and why Talos isn't allowed to be worshipped. No worship is no power, and therefore no Talos. 

But an aspect of Lorkhan exists in every culture in Tamriel, even if he's portrayed as the Devil. Even the Devil is worshipped throughout religions, hence the existence of Daedra worship. Even in real life, Satanists still worship the Devil of the Christian religion, even through constant oppression via people of different faiths. Christians still worshipped god through Roman oppression. Faith persists through whatever happens to their religion. I'm sure someone out there still worships Tlaloc of the Aztec religion. So Lorkhan will always be worshipped, no matter what happens to his image.

In summary, The Stormcloaks are a bad option, but the Empire, who's too focused on the past to see how bad they're failing, is much worse. The rise of the Thalmor is inevitable, but Talos is and always will be a valid god and will always be worshipped.