Blaming the Dracs for Kentares is ridiculous. Except for maybe the FedSuns, every other successor state would probably have had a similar initial response if the same had happened to their head of state, especially the more unhinged ones like the Capellans and Lyrans. You just need to have the right individuals in place and they would have ordered the same thing

The only difference is that the DCMS was actually disciplined enough to carry out the orders thoroughly, and probably would not have chickened out like the other armies which are made of less sterner stuff and would probably have started refusing further massacre orders after the first several tens of thousands