It is really troubling to have to experience such a situation in the game this is why I can understand your standpoint.
Allow me to offer some suggestions on how to proceed with this type of situations if you still encounter them.
Since pillaging is the part of game mechanics, we cannot do much about that, but to say that you have to invest some time by making good tactic to make your enemy stop attacking you. Try to contact him, with a good, polite and friendly tone asking them to stop or ask some other alliances to help you with the war. There are a lot of open options to handle such enemies, but keep on mind that the main key to success is a wise tactic.
From Game Rules side - we cannot do much since I can confirm Kovomatix statement that Bashing rule was removed and there is no limit regarding pillaging anymore.
Have a wonderful rest of the day :)!
Super Game Operator
Thin Blue Line