Well the first obvious thing to do is to confront all of the "reasons" why black holes should be impossible with the specific evidence that black holes have been observed. I have posted this evidence many times, but it just seems to keep coming up.
Consider the bulk of published evidence showing that black hole event horizons have been observed, i.e.,
Narayan & Mahadevan, 1995;
Narayan, McClintock & Yi, 1996;
Yi, et al., 1996;
Narayan, Kato & Honma, 1997;
Narayan, Garcia & McClintock, 1997;
Narayan, Barret & McClintock, 1997;
Menou, et al., 1999;
Quataert & Narayan, 1999;
Garcia, et al., 2001;
Narayan & Heyl, 2002;
Narayan, 2003;
Yuan, Narayan & Rees, 2004;
McClintock, Narayan & Rybicki, 2004;
Narayan, 2005;
Broderick & Narayan, 2006;
Remillard, et al., 2006.
All of these papers combine to illustrate the difference between the hard surface of a massive compact object, and the event horizon of a massive black hole. A physical surface will radiate a thermal spectrum, an event horizon will not. An event horizon will pass through energy that would otherwise encounter a physical surface (i.e., energy seems to "disappear" into the black hole). Accreting matter will encounter a hard surface and flare, whereas accreting matter will encounter an event horizon and simply keep falling. All of these points are covered in this collection of papers, all consistent with an event horizon, and all consistent with the predictions of general relativistic models of accreting black holes.
So, in the context of the observational evidence, how do MECO's compare? Does an "eternally collpasing" object look like it has a surface or not? Observational evidence indicates that energy "disappears" into the black hole. How are those observations interpreted in the context of a MECO? What observational evidence would distinguish between a MECO and a black hole?