The princes and Shira are better suited for the job than Jinbe. And this situation won't likely happen again, because "the children are watching".
They aren't fishmen last time I checked. And I think it has to be someone like Leader (oh god, what is his name) from Alabasta, someone who isn't royalty. But that's in my view of how OP should be, others (including Oda) would probably be fine ignoring this.
Racism and hatred just don't dissipate instantly, particularly when it's clear above water (and under water with Caribou) some people hate fishman. This is a long, hard process, not something that should just miraculously change in one battle.