I was also just reading that the British actually sided against Barghash in his struggle for power against his brother, resulting in him living in exile for two years. I can see that being a big reason why he'd also not like Europeans too much. If you show him you're on his side. I'm willing to bet he'll be quite happy to cooperate. It's still Wednesday, you have until the end of the day to edit your orders ;) (I always feel better after rewording or tweaking my orders a bit on the final day :P)