I quite frankly am annoyed at how physicists (and worse, science journalists) natter on about “dark matter” as if they were certain it exists. It is a hypothesis proposed to explain differences between observations of the universe on a large scale and what our current understanding of gravity (general relativity) would predict. It is quite possible the differences are entirely explained by quantum corrections to general relativity (which the same physicists also expect, but can’t calculate for lack of a completely viable theory of quantum gravity).
In their defense there is usually a reporter between the scientist and us, and they could screw up the the spelling of their own names.