Do you think the old man is being honest when he challenges the fish to kill him?

In my opinion, the old man isn't really challeging the fish to kill him.... the fish is putting the old man in a situation that he may not be able to survive. None-the-less, had he died while struggling with the great fish, he would have considered it an honorable death.

“Fish,” the old man said. “Fish, you are going to have to die anyway. Do you have to kill me too?”

You are killing me, fish, the old man thought. But you have a right to. Never have I seen a greater, or more beautiful, or a calmer or more noble thing than you, brother. Come on and kill me. I do not care who kills who.