But even if the WG found out, doubt they would take away his title just for attacking a few marines in one branch. Especially the branch that no one else really views all that highly.
Also: Speaking of the anime, did we ever find out what was up with the prisoners frozen in the walls/ceiling of that one room? I remember reading about it in the manga, and we were all conjecturing on what it might be about. But here we are at the end of the arc, and I don't think any of the Strawhats have ever mentioned it again :-/