ok pirates will attack anything that get in thier way, but you can trick these devils with bounty, if you place bounty on someone else, and its the highest, the pirates will be more focused on attacking who ever has the highest price on their head,

now there is a problem with bounty because the more money means that if the pirates(or whoever) finish their mission, they will recieve all that money, and that could mean an even stronger pirate problem. the pirates do attack to a timed consistancy(sp) now as you are talking about, "2 pirate bases surronded by yours" well then you will be their target, you have to remember these are pirates and they want what you have(money, resources, your destruction) so with this in mind, you have to counter with persuasion, avoidance, or brute force