Well we don't need to mention akainu fans, the simple argument that akainu will fight Luffy is just a hunch/assumptions, his whole argument revolves around the assumption/deduction, that he (akainu) will face Luffy, see, It's not even a concrete thing, but an argument based on assumptions, and that's what kills me with laughter, I mean, I don't even have akainu above: Shanks, BB, Dragon and even Big Mom, it would be an incredible throwback to the plot if Luffy facing someone weaker than Kaido and BB, akainu has no declaration of strength, so I as a reader can't go around assuming he stands a chance of being considered stronger than the characters I mentioned above.