Evidence that the key assumption made in discovery of dark energy is in error

> Our understanding of cosmology is built on top of observations yes, but those observations are stacked up against experimentally verified data,

And a cave man who was curious would also do lots of observations. He would observe by the river, by the big tree, by the big rock, up at the top of the hill. No matter where he goes, he can breath. He can feel the air when he swooshes his hand through it. He keeps collecting data for 50 years, and everywhere that he can check he sees the same thing. Therefore, using the same level of proof you propose, he can conclude that there is air everywhere. Someone else might come along and say, well, he is assuming that the universe is the same everywhere, then checking where he is actually able to measure. The same is true for you, you can't make measurements of any kind beyond the CMB. We have no idea how large the universe is or how much of it we can observe. We can assume the stuff we can't see is just like the stuff we can see, but it's an assumption.

> There's also nothing inherent to an anisotropic universe that would rule out expansion

Sure there is. We might just be in a location where stars are diverging. There's no way to distinguish an area where the visible universe is diverging from one where the universe is expanding. Why do you think people are so excited about accelerating expansion? It would be evidence of expansion rather than divergent proper motion.

In fact, lets say there were some kind of massive explosion in space. If you took measurements from near the center of mass from the explosion after a long time, you would see the things that are far away red shifted more than things that are near by. Why? The things far away were the things which were ejected from the explosion with higher velocity than things that are nearby (that is why they are farther away now).

It's incredibly frustrating replying to you, because your arguments are fundamentally anti-science. Everything you're saying can basically be condensed down to "Well, we though we've known things before, and we think we know things now, but we can't EVER REALLY BE SURE, can we? It's all an assumption!"

Trying to compare our current understanding of the universe to that of a cave man is quite silly. We've nailed down quite a bit of the why and how of the structure of the universe, the laws of physics, etc. It's not perfect, there's parts we don't understand, and there's parts we may never be able to understand, but the scope is so much broader and understanding so much deeper that trying to act like it's meaningful to compare our understanding vs. that of a cave man is so disingenuous.

A cave man would have no idea why that would be the limit of his observations - no understanding of physical laws that would make it so. But we understand why there are limits to what we can see. We understand that there is a maximum speed for a massless particle in a void. We understand why we cannot examine objects under a certain size - because the energy requirements would literally create a black hole if put into the space needed to see. A cave man could not understand why there is not more out there for him to observe. We can.

>Sure there is. We might just be in a location where stars are diverging

You seem to be misunderstanding either the meaning of the word "inherent" or the phrase "rule out". An anisotropic universe can 100% be expanding. It can also not be expanding. But you were previously arguing that our (evidence backed) belief that the universe is isotropic being incorrect would immediately rule out expansion, when it simply isn't the case. It's also not particularly relevant, because all evidence points towards the universe being isotropic.