@demrador I think Tanzawa's main issue with the 6th gen is that THEY killed Jou-kun instead of somebody outside the gang. Though I guess given the extraneous circumstances it is does seem like an insignificant detail to be hung-up on.
@Ikarus The fact that the 6th gen killed Jousuke isn't widely known, Kaname and the 7th gen leadership heard from Acchan and he knows because he said he was there.