I don’t know enough to have an opinion, but my hope is that dark matter does not exist. It feels kind of like Einstein adding a cosmological constant to relativity to keep the universe static. (If that sounds familiar, it’s because I lifted from your “4 Mistakes” post.)
Ethan, if dark matter is attracted to itself and to regular matter only via gravitation, why does dark matter form haloes around galaxies rather than clustering into their centers? Why is it not thickest in the centers of galaxies?