You can use them to show disagreement, but if you do it on ten posts within a few minutes or always down rates a certain person/group of people, then it's pretty clear that you're just using it to pick on people and not using it to show that you have a strong disagreement with something they said. This is what we have taken issue with as far as I know. That's the way it has been abused. That and petty revenge sprees... ): If they show the same smite to people by talking instead of giving smites, we will notice if they're picking on them as a person or just want to argue against what they wrote in that specific post.
So you can disagree all you want, but you can't be going after a single person all the time, or throw bad ratings on someone simply because you don't like that person. That's the issue. We've never cared for a smite or dislike that appears sometimes now and then because someone said something someone else didn't like. (Which mainly happens in discussion threads). If that was the case, we would probably have lots of banned people and warnings right now :D