Declaring something dead is just the most readily available form of criticizing. Being critcal makes you appear competent without too much effort. And if you cannot follow the critizing person's judgement he/she can still look down on you and pretend to have just higher standards. It's a well-known trick in the corp world, and I have seen it described in books as well. That's why doers are weak in bigger companies, because most things you do are easily attackable, in their early feeble stages. And you just deliver something others can be critical to boost themselves.