I too would like to see a negotiate and defend option instead of only being able to ignore this. Along the lines of the poacher quest negotiate/bargaining,
1. This caravan is under my protection,
A. Please leave it alone with this money (bargain)
B. Leave it alone or I will be forced to attack - strength of parties is looked at by the opposing lord, hit on relation with lord or lord and clan/kingdom.
C. Attack without warning, definite hit on relations.