You have to be a grade A retard to support the Stormcloaks. Its already been said that this plays into the hands of the Thalmor, but beyond that you need to ask yourself what is Ulfric even fighting for?
The answer is the Imperial Cult. He isn't fighting for a return to the days of Shor worship. He is fighting for a religion that was imposed onto the provinces after the Oblivion Crisis. Ulfric is thoroughly imperialized and throwing a shitfit that he can't worship Talos even though Talos has open shrines all over the province.
I am sympathetic to the idea of Skyrim's independence but Ulfric is a belligerent retard.