I'm a bit puzzled by your stated position.
If you're saying that Windows is fine for non-critical applications, fine. I don't think anyone would disagree with you.
If you're saying that Windows is fine for safety-critical apps, you're just plain wrong. You've given examples of reasons why Windows becomes unstable (people fooling with them), but there are plenty of other reasons: 3rd-party drivers for NICs and graphics cards spring to mind. And if the Windows machine is connected to a network, you're in real trouble.
Even with a plain-vanilla Windows machine with no 3rd-pary drivers, and no network connection, only a fool would trust his life to it. This is, I think, unarguable - it's just the wrong platform to use.
Steve