I think that's a stupid glitch in the game though. Paarthunax himself says that Alduin (their king) has been leading them to evil ways. The fact they keep attacking makes no sense, even if they're evil they act like the killing of their leader meant nothing at all.
He also says (spoiler tags are your friends)
Spoiler
that he has to go talk to the rest of the dragons, because they're an independent lot. It's not like he can magically make them all decide to stop flying around killing stuff.

I am the most popular dragonborn ever!! The BBC even made a TV broadcast from the Throat of The World, featuring me, the Stormcloaks, the Imperials, the Greybeards and everyone else, too. Even Paarthurnax came back from the dead just to tell me what a great show it was. I lolled hard when Byrnolf tried to steal the moderator's microphone. Oh, that was so funny.