I do not doubt that muons can be distinguished from energetic electrons with sufficient checks. One thing I suppose might be apparent would be the decay at the end to an electron. The question here is whether Holmlid and Olafsson's custom-built apparatus, discussed above, is sufficient to distinguish between muons and electrons and whether they've done the necessary checks to rule out competing explanations. Even if the apparatus were in principle adequate (I doubt it is), I would not trust the two to be diligent enough to attempt to falsify their preferred explanation (muons). An independent expert in measuring charged particle radiation would be what is needed here.
Those two are talking to a guy from CERN who just doesn't beleive them. How could he, if a few hundred dollars of equipment can do the same thing that the 10 billion dollar Large hadron collider can do.
Yes there is a gulf in belief afoot here.