Would they not suffocate almost immediately and die from that rather than seeing them running and screaming like you see them in the movies? If so, isn't napalm more inhumane and cruel than a flame thrower?
I don't know anything about napalm. Before my time (isn't that Vietnam-era?)
People don't die instantly from being engulfed in flame. Usually it is the smoke or fire inhalation that will slowly kill them as they suffocate or they die later on from the amount of burns they have on their body. Burned skin tightens on the body and can suffocate someone if it isn't cut open. People usually die if they are burned over a large percentage of their body from infection, not from the actual burns itself. It is a slow painful awful death. Some people do survive large body burns but they are deformed and go through a lot of pain.
So no people can't die instantly from fire.
This is enough time to react and run around (stop, drop, roll, etc.). Moving around moves the flames and pushes air into the lungs. So, in short, I person can still get oxygen while burning alive.
Usually the fire will kill the person, burning their tissue and causing "death by loss of plasma" or heatstroke. All of this happens rather quickly, so it is actually quite accurate to say that "Burning by fire is the cause of death by a flame thrower."
With napalm, a large area is burned at once, and individuals are much more likely to die by carbon monoxide poisoning (suffocation) if they are not caught in the fire itself. Flame throwers actually shoot out a flammable gel or gas that is similar in nature to napalm.
In all, war, in all of its forms (whether death comes from napalm, flame thrower, bullet, or knife) is inhumane in that it's primary execution is the loss of human life.