And whats wrong with fighting for your right to be called High King? What's wrong with fighting for your right to openly worship Talos? Why must Skyrim obey a weaken Empire to weak to rule? Skyrim is Nord land. The Nords should rule, not the Empire. Unfortunately a civil war is often necessary to root out corrupted politicians who refuses to step down from the bench. Torygg was a corrupted High King who worried more about Imperial coins then his countryside, and Ulfric witness this with his own eyes. While Torygg was intrigued about Ulfrics Ideas about Skyrims independence, he done nothing about it. Imperial coin was way more important than without.
The Nords do rule Skyrim, unless you can point me to a non Nord ruler of a Hold? But you forget there are many races in Skyrim, Skyrim has been a part of a Cyrodiil Empire since the Second Empire under Reman. Is a Dunmer born in Skyrim any less important than a Nord born in Skyrim? To the Stormcloaks yes, there is a difference. To the Imperial Empire, no there isn't a difference. I support racial equality, something that the Empire spreads.
The High King can't declare independence without the backing of his Jarls, he would need Ulfric to actually ask him. Torygg was Jarl of Haafingar, the Nine Holds are all largely independent. He can't force anything onto them, the Pact of Chieftains is a Nordic tradition. He would need the support of his Jarls, otherwise all he can do is make Solitude independent.
You also have no proof of anything bad against Torygg. He killed Torygg as a mere message to the other Jarls. Imperial coin had nothing to do with it, Torygg was the High King of Skyrim, last time I checked, Kings had money. You have no basis on which to call Torygg corrupted. The man greatly respected Ulfric and would of more than likely gone independent had Ulfric, simply asked him. You're willing to twist around every word, every person to try and make Ulfric Stormcloak look like a saint. The man is a murderer, a coward and frankly he's an idiot. He can't even look after his own Hold. Look at Windhelm, the place is nothing more than a slum, stockpiles empty, the city is basically bankrupt, they can't even investigate a serial killer. You don't see that crap in Solitude.
"We loved Talos more than the Imperials" No, Talos proved his power of the Thu'um the Nords still raised an army against him.
Now lets take a look at how the Imperials are tyrants forcing the Nords into 'chains'
War of the Red Diamond, Skyrim takes up arms against the Empire and the Dragonblood Empress. Empress Kintyra II, captured and died in captivity. Skyrim gets away with this uprising, the evil Imperial tyrants didn't force the Nords into chains and oppress them.
War of the Bend'r-mahk, Skyrim invades High Rock and Hammerfell, destroying the combined armies and taking many miles of land. Skyrim still hasn't returned that land, they just invaded two provinces of the Empire, killed Imperial citizens and captured land for themselves. Skyrim gets away with it, the Imperials didn't come and oppress.
Now we take a look at what is happening now, "The Imperials are oppressing us" No, the Imperials weren't even bothering with Skyrim, they poorly enforced the treaty on Talos, and everyone who worshiped it, didn't even care, they all had their little shrines to Talos. Twenty six years later, Ulfric kills the High King of Skyrim, the rise of the Sons of Skyrim and the Thalmor spread like a cancer, dragging people off for even secret worship. Using the Civil war to roam around Skyrim freely, unchecked, unchallenged. Because Ulfric has forced the soldiers off the roads, who patrol and protect the citizens. Into Military camps and front line battles. Unable to even stop the Thalmor, twenty six years and the Thalmor were kept in line. They couldn't make an arrest without proof, without Imperial consent. The treaty didn't allow them amazing powers, it didn't allow them to kill and torture. They're using Ulfric to be able to do that. Any death of a Talos worshiper by the hands of the Thalmor is Ulfric's fault. Not the Empire's, twenty six years the Empire was in control and no problems with the Thalmor.
Ulfric rises up, and now there is a problem with the Thalmor. The Empire may have allowed them into Skyrim and the other provinces of the Empire, but it is Ulfric who gave them the ability to kill Nords and Imperials alike, with no one there to stop them, because their asset Ulfric Stormcloak is helping them do that.