Read again; I said, he is a potential Black Blade user. I did not confirm it. The rest of my argument revolves around the fact that he is a top-tier and that he broke King's defense, which Zoro couldn't with his CoA.
Chopper said nothing seems to hurt him. Not, nothing except when he was held by Marco.
Fans have to either acknowledge that a little bit amount of blood doesn't count as hurting someone. Or we count Chopper's attack against Queen and Marco's attack against King as more of Oda's inconsistency.
I talked about this before and I don't understand why some have a hard time understanding this or accepting this. Oda makes small changes to the manga all the time.