It seems like you're essentially saying "This argument is correct. Anyone who thinks it is wrong is irrational."

No, what I'm saying is, I haven't yet seen anyone provide any counterarguments to the argument itself, vs. "using arguments as soldiers".

The problem is that it's not enough to argue that a million things could stop a foom from going supercritical. To downgrade AGI as an existential threat, you have to argue that no human being will ever succeed in building a human or even near-human AGI. (Just like to downgrade bioweapons as an existential threat, you have to argue that no individual or lab will ever accidentally or on purpose release something especially contagious or virulent.)

Furthermore, even if you suppose that Foom is likely, it's not clear where the threshold for Foom is. Could a sub-human level AI foom? What about human-level intelligence? Or maybe we need super-human intelligence? Do we have good evidence for where the Foom-threshold would be?

It's fairly irrelevant to the argument: there are many possible ways to get there. The killer argument, however, is that if a human can build a human-level intelligence, then it is already super-human, as soon as you can make it run faster than a human. And you can limit the self-improvement to just finding ways to make it run faster: you still end up with something that can and will kick humanity's butt unless it has a reason not to.

Even ems -- human emulations -- have this same problem, and they might actually be worse in some ways, as humans are known for doing worse things to each other than mere killing.

It's possible that there are also sub-human foom points, but it's not necessary for the overall argument to remain solid: unFriendly AGI is no less an existential risk than bioweapons are.