I do, however, believe that Dirty is often inconsistent. He recently agreed with the idea that the balance in SoD largely depends on randomness. And then, shortly after, he wrote that Diplomacy is bad because it can turn the game around at any moment.
Well, let's say someone very valuable joined your side. But your opponent, on the other hand, may have found Cartographer. Or DD found it.
Banning various overpowered cards, like Diplomacy, is dangerous because it undermines this unique balance, which consists of a number of different overpowered cards. There shouldn't be too few of these overpowered cards in the game – otherwise, the remaining overpowered cards become too strong.