So Arngeir sent me to talk to Ulfric and Tullius. I hadn't even been to Windhelm yet, so decided to go to Ulfric first. After his conversation/speech with that one guy, I was prepared to ask him about going to a peace treaty at High Hrothgar, but there doesn't seem to be any dialogue option for it, only ones about joining the Stormcloaks. Is joining the Stormcloaks a requirement for this? That was actually the side I was planning on taking, just not yet.

I have the same problem.