My take on all this (based on all the information that we are currently aware of) is that Tanzawa, Kaname and the rest of the leaders of the 7th generation are freaking nutjobs for supporting the 5th and not taking any action to prevent him for causing even more harm to innocent people. Even at this point in the story Tanzawa supports Jou-s action in the past, just because he and the rest of the 7th gen were safe while Jou was causing havoc left and right. Yoshiki was at least trying to protect everyone (not just Kilihito members) from this madman, even if it means he would become a murderer and Yoshiki's action at that point were the main reason Kai managed to get so many people while Yoshiki and the rest were in juvi. And Tatsuya would have to be stupid to support Tanzawa and the rest of the 7gen in this war (assuming that he knows everything what Jou has done, not only the information Tanzawa gave him 30 chapters ago). But there is also a strong possibility that Kai was pulling all the strings back then as well, but we'll see about that in the future.