Well, early on in the one of the quest chains, Delphine tells you about "Secret Purges" The Thalmor conduct on anyone who doesn't believe what the Thalmor believe. The Thalmor report them as "Accidents" so it is hard to tell who is telling the truth, but the Elf who helps you get into the Thalmor embassy seems to believe what happened to his family wasn't an accident.
Further, several Nords who sided with the Empire seem to see Ulfric as a power monger, which he seems to be. He was supposed to be a greybeard, he studied with them, learned the way of the voice, broke his commitment, which wouldn't be so bad but he doesn't follow the way of the voice, using Thu'um to murder people like the High King. Using it for personal gain. Of course the Nords that sided with the Empire aren't the most objective people in the world, but at least they can see the bigger picture.
On the other hand, while the ancient humans were indeed enslaved by the ancient elves, the ancient humans also committed acts of genocide, going so far as to almost push the snow elves to extinction, forcing them to ally themselves with another group of elves the Dwemer (Who are Dwarves, but still technically elves, just like the Orcs are technically elves). So I can see why the Thalmor hate Talos, who almost destroyed Elven kind on Tamriel, still you can't deny he is at least somewhat god like, since praying at his shrine gives you a blessing.
And as we can see from Oblivion, gods can just give their powers to someone else, in the case of Sheogorath who gives his godhood away to our characters from Oblivion.
In the end, it is really hard to judge Ulfric, the Empire promised him and his miltia that he could worship Talos again after freeing Markarth, they were forced to go back on their word because the Thalmor caught wind of it. Still, instead of attacking the Empire, they should be working with them, preparing for the next war, and preserving Talos's Empire for when they CAN worship Talos again.
Further, several Nords who sided with the Empire seem to see Ulfric as a power monger, which he seems to be. He was supposed to be a greybeard, he studied with them, learned the way of the voice, broke his commitment, which wouldn't be so bad but he doesn't follow the way of the voice, using Thu'um to murder people like the High King. Using it for personal gain. Of course the Nords that sided with the Empire aren't the most objective people in the world, but at least they can see the bigger picture.
On the other hand, while the ancient humans were indeed enslaved by the ancient elves, the ancient humans also committed acts of genocide, going so far as to almost push the snow elves to extinction, forcing them to ally themselves with another group of elves the Dwemer (Who are Dwarves, but still technically elves, just like the Orcs are technically elves). So I can see why the Thalmor hate Talos, who almost destroyed Elven kind on Tamriel, still you can't deny he is at least somewhat god like, since praying at his shrine gives you a blessing.
And as we can see from Oblivion, gods can just give their powers to someone else, in the case of Sheogorath who gives his godhood away to our characters from Oblivion.
In the end, it is really hard to judge Ulfric, the Empire promised him and his miltia that he could worship Talos again after freeing Markarth, they were forced to go back on their word because the Thalmor caught wind of it. Still, instead of attacking the Empire, they should be working with them, preparing for the next war, and preserving Talos's Empire for when they CAN worship Talos again.