GUTs, despite containing "theory" in their name, are all hypotheses at this point. Hypotheses often multiply without improving our understanding very much, because most of them are wrong. That's why we should try to avoid high levels of confidence in unsupported hypotheses, but we should not avoid generating them altogether, because we have to find the correct ones somehow.



Sean Carroll, like many theorists, constantly looks at new submissions from other theorists on arXiv and in print journals, which includes numerous alternative proposals for dark matter. Everyone wants to be the person who blazes a new trail, but no one wants to be the person who wanders off the trail and gets lost in the woods. Sean, like many astrophysicists, has made the judgment that the risk of getting lost in the woods in this area is no longer worth the reward of blazing a new trail. At this point, you seem to be complaining that Sean has a higher level of confidence than you do in exotic dark matter, as though your level of confidence were more appropriate despite your unfamiliarity with large amounts of the evidence and the fact that cosmology is actually his field. Who's the arrogant one supposed to be, again?



I would not think anything special about such a hypothesis; I've heard many that start in just that way. This is how generating hypotheses works; again, no one is putting a high level of confidence in such constructions right away. If you don't like this system, feel free to come up with a better one; I wish you the best of luck.