it is not the fact that bitcoin is dead the people sometime says wrong statements which is disturbing for the users but when the users of bitcoin become attached to this then they realise the importance of bitcoin and they are doing best for this crypto currency they are not come in the people talks in the society. through this action the bitcoin become more familier among the other users as well.
They do that to cause fear and panic in the system causing the faint hearted ones to sell off their bitcoins for cheaps so that they can buy it all for themselves when the prices of bitcoin takes a tumble. Its an old trick by the bad guys and they seem to be succeeding in recent times.
I would also add that it's fear.. people are not brave enough or have courage enough to take risk on something that doesn't provide historical data to help them feel better about their investment. so this is why they scream "its going to crash!" or "its dead!"