Be careful with your use of the word 'murder'. Here in Florida I have the law on my side if I shoot and kill a home invader. That's not murder either.
Obviously you don't agree that the island is their home and they have a right to keep intruders out by any and all means. The two liquored up fisherman, with all the knowledge of the consequences of approaching that island, knew the rules.
So either let 'em rot or invade and conquer the island and impose outside rule.
The two men were foolish. But they should not have been murdered. While I think these people certainly ought to be allowed to continue to live on their island without outside interference, no one on this earth has a right to murder. Their island or no. Breaking and entering into a home is NOT the same thing as landing on a beach. No one has a right to murder. No one.