In the face of the Scenario tab in the Game Editor, bottom left, there are options to modify barbarian activity. This is a different tab than the rules tab and you will find many things you can change, alter or tweak. Some have found however, that even this is still not enough to suit their tastes, so as well in face of the rules/general tab find on the right side, three options to 'set' the default barbarians. Such as warrior etc. Here place 'none'. This effectively eliminates all barbarians from entering the game no matter if barbarian camp still show up, they will be 'empty' and you can roll over em and pick up some spare cash.
Happy Modding!