IMO any kind of posts which is made just to spread FUD about bitcoin should be deleted on sight or at least moderated to some degree. but I might be biased.
So you want to enforce almost nazi moderation on people? And be like: "If you don't like it - delete it?" That is not the way imo.
Some FUD stories are based on solid ground, some are not. Deleting everything slightly FUDish is not good option.
Of course, I am not against deletion of some posts\topics if someone is posting total nonsense.