I agree that "hurtful" threads should be deleted.
If by
controversial you mean that not everyone agrees then there is absoulutely nothing wrong with controversial threads imo and they should be allowed to stay and stay open so that ALL points of view are represented. If you allowed only one opinion and everyone had to agree otherwise the thread would be closed and/or deleted, then we wouldn't learn a thing and we may as well not have discussions.
The threads are sometimes MADE controversial when they really aren't just for the purpose of disagreeing with someone a member or a group of members does not like for whatever reason. This is what I dislike the most. It happens constantly and then the fact that the thread is closed is even blamed on the person who was the object of the so called controversial post when the reason it is usually closed is because the ones who disagree for no real reason break the rules, get disrespectful, snide and rude and admin has no choice in order to keep peace on the forum. It is such a shame when this happens imo.