Just the opposite: you need the CoC to make sure they do get kicked out. Because for example if the writer of that comment is friends with the moderators of the forum, they might get a slap on the wrist and allowed to continue. Having a written CoC lets people know that the mods can be held accountable to the document. Another example making the same point, this time of actual harassment being ignored: https://www.youtube.com/watch?v=oxLENeCf3OA