And Ulfric respected the High King enough to allow him a one-on-one fight. The High King accepted, out of respect. So what if Ulfric brought this to home, now he has in control a General with the power of a god! And an army of DRAGONS!
BOTTOM LINE
Any side that the Dovahkiin chose would have won the civil war and defeated the Thalmer. I picked the side with enough balls to get it done in a respectable amount of time.
The problem is, Skyrim would currently be mopping the floor with the Thalmor if Ulfric wasn't a head-strong idiot.
This would occur if he asked Torygg to declare independence:
"Torygg, I request that we break away from the Empire, so we are free from Altmer oppression, and can worship freely."
"I respect you, Ulfric, and your motives. I think Skyrim stands the best chance united as a sovereign nation, and defeating those that would try to conquer us."
Bam, that's all he had to do. Instead, this happens:
"TORYGG! I WANNA KILL YOU! YOU WANNA DAI!?"
"I..... um.... accept your challenge?"
"FUS RO DAH! Now Skyrim no longer has a king, half the people hate me, and the other half are going to get launched into a blood civil war, in which countless hundreds will die against the Thalmor and the Empire."