walks like a duck, and quacks like a duck, there is a high probability that it IS a duck.
For example, that muslim kid in California that slashed 4 people the other day. Media and police are saying that he was just disgruntled, and that the attack was not a terrorist attack.
That line of thought has been used on a number of attacks by muslims. Even when they person responsible left a trail of evidence, FB posts, written documents, statements, that the attacker was doing the will of allah, .gov still won't admit the terrorist angle.