Okay, so... apparently those lines went right over peoples' heads. I'm not sure how. But "If ye be a true laggard, I'd be a whoreson fer talkin' down of ya. Can't let ya go stickin' dubloons up yer nose or jumpin in' the water because ye see a pretty fish, so I guess I HAVE to come along" means:

"Man, if you're actually retarded, I'm going to feel bad for insulting you. I can't let you go sticking coins up your nose or jumping in the water because you see a pretty fish, so I guess I HAVE to come along."

I... kind of assumed that a lot of that could be inferred from him asking if Devil Fruits cause brain damage.