Okay so im on the quest for the republic part 2 and my first objective is to enlist the aid or destroy the great khans. Now iv killed karl got the support of the two drug dealers and melissa now all I have to do is convince papa khan to support the NCR, problem is the quest screwed up now im at the part where I got the history book on the khans but for some reason the game thinks I still havent broken the Khans of thier treaty with legion. no matter what do I cant get him to ally with NCR. Now I looked up what to do on the wiki and it says kill papa khan and Regis will ally but yet when I do this Regis doesnt have that option all I can say is goodbye. Has anyone elese encountered this problem and if so how do I get through it or will I have to wipe the Khans out.

It seems you will have to Kill Them all