The context of the thread was police officers being trained to be wary of knives. Imagine two comparable traffic stops where in one case the "perp" has a concealed knife, and the other has a concealed gun. A single officer in each case faces a very comparable risk at close range. I'd argue that at three feet, the officer is much more likely to be killed by a concealed knife than a concealed gun, assuming that is the perp's intention (and the perp has already been asked to get out of the car).