The question in the op, although posed in a rhetorical fashion, is a legitimate one. Something happened to make this person act like this, we just don't know what. It's overly simplistic to dismiss him as an idiot or to call him names, that may serve a purpose in getting our own frustrations out, but it's hardly getting to the root of the problem.
Frankly it's an argument, as if we needed another one, for the removal of more cars in general from our roads and for the increased provision of safe, reliable, integrated public and active transport systems. A frustrated person on a bike or a bus may cause some disruption but is unlikely to impede the emergency services in the same way, and fewer cars both driven and parked on the roads means easier passage and better overtaking opportunities for large emergency vehicles.