Sometimes an inappropriate post is triggering to many users. Even if it is hidden, we see many people unhide it and reply to it anyway. Before we know it we have 10 posts of heated discussion mixed in with the intended discussion, and we have to start deleting about 10 posts to finally get people back on topic. Deletion then further angers them, as they have already formed an opinion and feel it is getting censored.
One thing which might help here is to disable the possibility of unhiding a post until it has been edited when a post has been flagged as inappropriate.