Well if you remember the Empire was victorious in the War but signed the White-Gold Concordant(for those of you who don't know it's the legal document that banned the Worship of Talos) To bring peace as the war was slowly weakening the Empire, I don't agree with the terms of the Contract but as a loyal citizen I must abide by it. And at a time like this the Empire must remain resolute as the Thalmor and Dominion grow stronger. Which is why we can't have people like Ulfric Stormcloak trying to divide Tamriel further.
Also it extends beyond personal belifes and crosses into what's best for Skyrim and Humans (Beast Race's also) of Tamriel. The Aldmeri Dominion is ruled by the Altmer (or High Elves) whom are the most rigidly caste people of Tamriel, assuming they were to control Tamriel what would that do for Imperial, Nordic, Argonian, Khajiit, Orcish, Reguard, Breton way of life in Tamriel? Obliterate it!! It would go back to the time where the Alyied Kings ruled central Cyrodiil before Alyessia rebelled. There was no Human way of life just Alyied, now imagine that spread all over Tamriel. Look at Valenwood, it was taken by the Dominion in force and many Wood Elf clans and families, were purged, destroyed and out right wiped out. Are those the ones you want ruling Tamriel?
Don't fight just for the right to be a free Nord, or the right to Worship Talos, Talos is Hero, God, and King in my opinion of Elder Scrolls lore, but in the end what does it come down to? Survival, which is why the need of the many must be put before the needs of the few. If this contract helps the Empire to survive and rebuild to ensure equallity across Tamriel then who do you think you are to stop prosperity? It may not be your favorite thing at the moment but in the long run Skyrim and Tamriel as a whole will be stronger.
Also, assuming Ulfric wins the war, do you think he could really secure Skyrim and re-build a new Government with only Mercanarie's and just average citizens for soldiers? The Kingdoms of High Rock (Wayrest and Daggerfall mainly) would be more than a match for an untrained Rebel Army like Ulfric's. Not to mention Elinhir of Hammerfell they would not hesistate to challange Ulfric for Skyrim either.
You have to think beyond the games programming and think realism, thats what makes the games so fantastic there's more to it than meets the eye.
This is just a rant to make you all see how much better the Empire is, if this doesn't make you want to join than nothing will.

Thank you for reading this.