You just don't get it.
There's a difference between liking and disliking a song and THIS pairing.
I've said it before and I'll say it again.
Consider FUNimation taking a song that sounds similar in tone, melody and lyrics to the Sesame Street opening, and setting it to One Piece.
That's the case here.
Hey, I'm fully willing to admit to not getting it. I'm no expert on how the politics of these song choices work, nor can I understand the lyrics without consulting a translation, and on that subject, to me, they feel rather in-line with the series themes with their talk of adventuring, making memories, and encountering occasional hardship, if perhaps not expressed in the most ideal manner. I mean, my view is pretty much that it's not the ideal song, but that fact does not effect the content of the actual episode. Toei is still giving Oda's series a decent adaptation, and life will still go on. Again, perhaps I don't get it because of my ignorance, and because that I can't quite find it easy to compare the brief opening jingles or what have you of American children's programming with hiring mainstream or niche music bands and setting proper vocal songs that will be sold in stores to expensive animated sequences.
If you don't see the reason for fan "rage" [or as I like to call it "criticism of something really fucking stupid"] I would pose the question, did you ever say anything negative regarding 4Kids and their choices?
I'm going to be honest, I have never seen a full episode of the 4Kids One Piece dub, only clips here and there, and peoples' writings and rantings on it. Again, I feel it hard to compare a brief opening song which doesn't effect the content of the episode itself, to over-editting and dumbing down that very content to the point where it makes a mockery of the original material. I mean, if the 4Kids dub had used the One Piece rap as its opening but everything else was stellar, A+ quality work I'd be rathered annoyed at the opening, but not to the extent that I'd be constantly going on about how awful it is and making up my own euphemisms for how crappy I think it is. I'd comment on how unfortunate the choice is and generally move on unless my feelings needs to be brought up again. I guess it's because I'm not too confrontational over stuff like this, and am usually pretty forgiving. As long as the actual episodes still do justice to the original manga and still manages to entertain me in a good sense, everything is cool in my book.