Disagree was never a negative rating.
No idea how to make that happen. Personally, I don't mind having the negative ratings. Many of mine were given by the turds who were banned due to negative ratings when they were confronted about their turd behavior. They come so rarely that it isn't even worth the time finding the post to remove them.
The ratio is all that really matters for users under 500 posts. Get too many of them and you'll get automatically banned. Since it takes some people a really long time, if ever, to get 500 posts having them removed may negate that setup. They really are only for moderation proposes. I can't possibly remember the post history of every single user and they work as a guide on what type of action should be taken.