All of these are valid arguments—or rather, would be if I as a GM allowed these things to become issues in my campaign. I am reasonably certain that in my years of gaming, I have managed to avoid these pitfalls, and I believe that player death is NOT a necessity to a well run, well balanced campaign.
In my games, in most circumstances and settings, I will not kill off a character due to an arbitrary die-roll. Unless they stray so far afield that I have no option, I will usually give them some way to survive. This is my stance.
In defense of this stance against arbitrary PC killing, I would like to offer the following points:
1) I do not like an adversarial relationship with my characters. As a GM, my job is to make the game fun. This often involves working WITH the players, to listen to their ideas and give even the most insane of them the chance (however slim) to succeed—especially if the insane idea is something incredibly cool story-wise, but maybe a bit implausible 'reality' wise. I don't have a lot of ego when it comes to the players 'beating' a scenario I devised. In fact, I can applaud them for it, especially when it is done with style.
2) I believe that a Character death should have meaning. Yes, I know life is cruel and deaths often do not have a meaning. But as an advocate of plot/story-driven adventures, I think that arbitrary death (i.e. "you rolled bad. You die.") should be avoided. I even like to avoid letting major NPCs get snuffed unless it is at some climactic moment. Death is dramatic and should be played as such.
3) I believe that Character failures should be met with fates other than death. This is where consequences for actions come into play. You may screw up and not die, but you lose in some other way: You get chewed out for failure, you lose one of your precious toys (ship, favorite weapon, etc.), you tick off someone who might have been an ally otherwise, etc.
4) I want players to be emotionally involved with their Characters. I want them to develop elaborate back-stories. I want them to develop elaborate personalities and quirks through game play. I want them to identify themselves and evolve through the course of play. This is MUCH more difficult in a campaign where arbitrary death is involved. I mean, if your character is likely to die every session, what is the point of putting any work into him? What is the point of getting attached if you're going to just roll up another?
5) Ultimately, I WANT my players to get powerful, to have a big impact on the world in which they live. That is the stuff of epic stories. To see a character grow from humble beginnings and rise to greatness. Yes, this means that it is more difficult to challenge the character, but a good GM can devise ways of doing that, usually by shifting gears to either 'epic' struggles (tougher and more opponents) or more abstract challenges (political maneuvering and moral dilemmas). This aspect works closely with the whole emotional involvement thing. If a character becomes powerful, he has more of a say in what happens in 'his' world—it becomes 'his' world.
6) In certain settings, death SHOULD be a remote possibility. In Star Wars especially, death isn't something that happens to the main PCs. They're the heroes, after all. They may succeed and fail, but they keep on going. Since Star Wars is my favorite system, it is only natural that that kind of attitude would prevail through my other games.
That having been said, there are some exceptions to the rule. Certain settings are inherently less-forgiving than others. And certain players sometimes leave you with little choice when their characters go off and do something incredibly dumb. In such cases? Well, I reserve that GM right to enforce the letter of the law. Thinking back on it, though, I can only think of one occasion where I actually allowed a character to die. It was (rather appropriately) in a Dark Conspiracy game. One of the players, Doyce, was just a bit too confident in his new Sorceror's skills. His first mistake was to walk off alone into a swamp, without telling anyone where he was going. In a horror-type setting, all of these things are a big no-no. He ran across a critter there in the swamp. Rather wimpy, actually...a fist-sized, blood-sucking urchin like critter that stuck into him and started sucking blood. For the next three rounds, his Sorceror completely ignored the pistol strapped to his leg and tried to use his magic to kill the demon-urchin. He failed. He got weaker. He failed. he got weaker. He failed...well, he died. I think that Doyce was expecting that I'd save his guy somehow, but...well, I couldn't think of any way how, other than deus-ex-machina. Considering the setting? I thought death more fitting. Doyce was surprised, but he took it with a good attitude.
So anyway, that's my stance on that, for what its worth.