I would agree with you if Ulfric benefited the people he served in any way long term. But the Empire isn't perfect, I admit. But they are better equipped to deal with the thalmor threat, and Ulfric seems more interested in fighting the Empire than the Thalmor. It could be argued that that's because of the CW though. As for the Empire's flaws, it is more justified because it sees the whole picture, and is the lesser of two evils. The Empire has a vastly higher population to take care of than Skyrim, and all of Skyrim isn't even committed to the STORMCLOAK cause. Roughly half of them are. Are they justified in dragging down the whole house to accomplish their own ends?