He's a Nord, Nords are a warrior race. It's expected that Nords would be arrogant and hostile, because that's what and who they are. Nothing wrong with that. At least Stormcloaks don't wear leather skirts.
And Ulfric is not completely wrong. He cannot be the High King until the Moot has declared him as one.
I sided with Stormcloaks too. I really can't wait for any Skyrim DLC news or any new TES game. I'd like to see a story around the return of the Dwemer or just how will Skyrim lead the Empire with Stormcloaks in charge. Or if the Thalmer will attack Cyrodiil/Skyrim now.