I read something a long time ago on how to persuade parents to let you do something. It went something like “Dad/Mom, you raised me to know right from wrong and to have a level head on my shoulders. Now is the time to trust you did a good job or admit you have failed”. I’m not doing that quote justice but you get the idea. You actually sound more level headed than your father. You have done some research on what makes a good beginner bike (admittedly to justify what you want but that’s ok ). Your dad is basing his decision on stereotypes. You could point out the stereotypical cruiser dude is in his 40’s, wears no protective gear and rides from bar to bar. Does that mean that’s what he will do? Course not. Same applies to you and sport bikes.
I suspect however the squid argument is just a front to justify what he wants. He wants a cruiser and would love to go riding with his son. Nothing wrong with that and it’s something you should think twice about before walking away from. There will always be time to get the sport bike later.