>Dark matter is a theory that fits the observations.
You are mistaking "theory" and "hypothesis". Dark matter is a hypothesis. It is unproven, it has not been observed. Describing this as a "galaxy devoid of dark matter" rather than "a galaxy where the dark matter hypothesis does not add up" is absurd. There is a difference between speculation about potential causes for observed phenomena and observed phenomena themselves.
Au contraire - in that galaxy the dark matter hypothesis really adds up. It's existence kills theories that "dark matter" is just an artefact of how gravity works.
A theory is a hypothesis that is well-substantiated by data. Dark matter is such a theory, those who believe otherwise almost always do not understand the data.
You are mistaking "theory" and "hypothesis". Dark matter is a hypothesis. It is unproven, it has not been observed. Describing this as a "galaxy devoid of dark matter" rather than "a galaxy where the dark matter hypothesis does not add up" is absurd. There is a difference between speculation about potential causes for observed phenomena and observed phenomena themselves.