The fin is your friend. It means you no harm. Do not fear the fin.
The fin has done you no wrong. It has always shown you kindness during times of peace, and restraint during times of war. You have no reason to suspect the fin.
The fin passed by you that time two seconds ago on the beach without so much as informing the shark it was attached to of your existence, much less the delicious flavor of your soft, supple, tender flesh. The fin would never do that. The fin is looking out for you.
The fin has no agenda beyond stabilizing the apex predator it rides against rolling. It doesn't care about tearing into the juicy meat that composes your body; it only cares about the z axis. How can it be concerned about the salty taste of the water perfectly juxtaposed against the sweet flavor of your muscles when it is so thoroughly indisposed with keeping its host upright? It can't, obviously. Think for a moment, jeez.
Really, though, you ought to put aside your prejudices. Just because a fin was ok top of a shark that turned around and proceeded to bite your brother's leg doesn't mean it wanted to eat you. That shark isn't a fin; it's a shark. Your failure to recognize the distinction is disappointing and, frankly, a little disgusting.
Oh, you're going to blame the fin because the shark that carried it, completely against its will, wasn't satisfied with your brother's leg and continued to tear into flesh and bone until he was completely consumed? That happened two minutes ago. When are you going to leave the past behind and stop letting it control your future?
Yeah, yeah, you can see the fin heading for you right now and you just assume, because of what's happened in the past, that you're going to be hurt, too. Stereotyping. That's just typical.
Well, how does it feel to be a bigot?