Sorry to hear your bad experience.
My suggestion is for you to not fish near bankers or fishing on banker holes.
I know that no body owns the river and that a person has the right to fish where ever he wishes but you got a boat and over 95% of the river system. The bankers only have limited holes to fish. Respect them by not boating on their limited fishing access hole.
With all the respect, I doubt that any bankers would come near a boat if they have other holes to fish on.

As for your threat, I have to remind you that bankers are like hyhenas, they will band together and most of them carry heat.
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Know fish or no fish.