Negative filtering would be a disaster. The power users do most of the voting and almost all of the reporting. If they all could block Ron Paul, those stories

Negative filtering would be a disaster. The power users do most of the voting and almost all of the reporting. If they all could block Ron Paul, those stories wouldn't get downvoted and, when offtopic, reported. This would cause the Ron Paul stories to take over the site for the 99% of users who wouldn't be using the filter.