Then don't do it. And if they try and force you, then raise a big stink over it. Protest the banker and ruler daily. Get your knights to support you, since the banker will be taking gold out of their pockets. Demand support from your duke to prevent the erosion of the lord's, and by inference the duke's, rights. If he won't support you, swap to another duchy that will. Sell all your food to another realm. If worse comes to worse, leave and go elsewhere. preferably taking your region and knights with you.
i.e. do something other than bitch, moan, and try to get the rules changed.
yes, Indirik - that's always been your answer to everything.
Rebel!
Doesn't work (outside of a few basket cases on Dwilight). You are usually the only voice, get to listen to a lot of "do it for the realm" crap, get to deal with fines, bans, threats, etc., get to try to rally silent, apathetic lords to your side
"Leave the Realm - and take your region with you!" - yes, if you are lucky enough to be in a border region, you can. And have them contact your new ruler, asking him to tell you to give the region back because it is "theirs", or to ban you if you don't. Which he often will.
Or you can penalize yourself by throwing away the closest thing to a Duchy you'll probably ever have in the game - a rural region with food to spare.
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The problem is, there are supposed to be checks and balances throughout the game. But most of them only work if the players stand up together as a group. If you have a realm where 90% of the players don't give a !@#$, then you have no checks and balance. You have one vocal knight against the Council and 90% of the realm who just wants you to shut the !@#$ up with your letters of protest so they don't have so much to read and can click their buttons in silence.
Your suggestions are based too much on the "theory of BM", but ignore the practical side.