I've seen some treatments in the scientific popular press (podcasts) that consider the possibility that dark matter can be explained by an error (or new term) in our understanding of gravitation & mechanics. I don't see anyone (in the podcasts) considering whether our understanding of "emission" or blackbody radiation were complete. Why are scientists more willing to consider new laws of mechanics than consider we don't know everything about how "regular matter" reacts with or emits photons. I'll admit that some of my "gut feel" is in a guttural reaction in college to the implausibility of a T to the fourth power in Stefan–Boltzmann law.
If the full answer where to be found in this P.SE question, I'll study it in greater detail.