Imagine you are in a room. There are two other men in the room with you, one rich and one poor. The rich man is holding a gun to the poor man's head, and asking you to tell him to pull the trigger.
Your natural reaction, I hope, would be to tell him to drop the gun. You do so, and the rich man's face falls. His gun doesn't.
"Ah", he says, "but this man is dangerous. He wants to hurt us." You look at the man, half-starved and dressed in rags. He doesn't look like he could pose a threat to anyone, let alone the rich man with the gun in his hand. "He doesn't look like a threat to me", you say. "It looks to me like you're the one posing a threat to him."
The rich man looks puzzled, and beads of sweat start to form on his brow. He mops them with a handkerchief, with his other hand. Suddenly, his eyes brighten. "He is a threat," he says, "he has a rocket launcher."
You look at the man. He doesn't seem to have a rocket launcher on him. "He doesn't look like he has a rocket launcher," you say. You remember that you know someone who is an expert at finding rocket launchers on people. You call him up, and he arrives.
The rocket launcher-finder begins searching the man, but he finds nothing. He continues to look, but the rich man, getting increasingly agitated, tells him to leave. He, confused, does.
"See?" the rich man says.
"Hang on," you say, "you haven't shown me any evidence that this man has a rocket launcher on him. Either show me the evidence, or put the gun down."
The rich man gulps nervously, his eyes flickering around the room. "Oh, and another thing," he begins, "this man and his friends are being tortured by my friend. I have to shoot this man so that I can save his friends."