Well, I don't know about photons, which can interact via the EM force. Neutrinos, on the other hand, only interact via the weak force and have a very low cross section for interaction. Therefore it's not unreasonable to say that they can cross intergalactic/stellar distances without interacting.
Jerry seems to want to lump neutrinos into the "gap-filling theory-patching stopgap" category he uses to tar-brush the dark matter hypothesis. The point Tim Thompson and I have made is that unlike dark matter (so far) neutrinos have been directly observed in experiments. Tim gives a good account of why they were first proposed by Pauli, so I won't repeat all of that here. The point is that when a beta deca occurs (the classic case being Co-60) the original researchers only saw the electron moving off in one direction, and that electron did not carry all of the available energy. If one believes that momentum and energy are conserved, then something needs to be moving off in the opposite direction from the electron to carry that energy and momentum. That something needs to be nearly massless and be very difficult to detect. Both apply to the neutrino. The fact that it was some 20 years before neutrinos were detected doesn't make them any less real.
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin
"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee
This isn't right. This isn't even wrong. - Wolfgang Pauli