In a time like this the negative news even sells better than the positive news..you can not stop them and you dont need to stop them because they are indirectly working for you by giving publicity to bitcoin.
I don't even think there should be a conscious effort from some quarters to try or attempt to stop negative publicity about bitcoin because they rather give bitcoin the opportunity to outdo the negativism and flourish as has been the case on several occasions. If they couldn't cripple it in its early stages I don't think they can now because the entire world is well aware of it and it's capabilities.