The point of the ignore list, is that a lot of game chat abuse is a gray area. Some people might not like the way a person is chatting, others may have no problem with it. So in cases like that, it is very useful for players to be able to self police and get rid of chat in most cases.
For cases where the poster is saying something that goes against the community guidelines or breaks other rules repeatedly, then an actual punishment can be handed out. But as I said, I'd prefer to see a system of self policing left in place for most cases.