Actually, you can spell out the argument very briefly. Most people, however, will immediately reject one or more of the premises due to cognitive biases that are hard to overcome.

It seems like you're essentially saying "This argument is correct. Anyone who thinks it is wrong is irrational." Could probably do without that; the argument is far from as simple as you present it. Specifically, the last point:

At minimum, this means any AI as smart as a human, can be expected to become MUCH smarter than human beings -- probably smarter than all of the smartest minds the entire human race has ever produced, combined, without even breaking a sweat.

So I agree that there's no reason to assume an upper bound on intelligence, but it seems like you're arguing that hard takeoff is inevitable, which as far as I'm aware has never been shown convincingly.

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?

I think the problems with resolving the Foom debate stem from the fact that "intelligence" is still largely a black box. It's very nice to say that intelligence is an "optimization process", but that is a fake explanation if I've ever seen one because it fails to explain in any way what is being optimized.

I think you paint in broad strokes. The Foom issue is not resolved.