"no one has yet justified why its acceptable for collectors to collect self penned songs from traditional singers but not from revival singers,"
Sorry Cap'n - must have dozed off.
Your point appears to be based on a misconception of what folk song collecting is about.
For a start - no self-respecting collector I know would ever have based their work on anything as subjective as good and bad; they/we collect songs in order to get an insight into the folk traditions, through its material and (hopefully), through discussions with the traditional singers. A song made by, say, Harry Cox (I may be mistaken, but I seem to remember he made a couple of songs) tells us much about the tradition and how it influenced the creative faculties of the singer. On the other hand, a song by MacColl (whose writing I much admire), does not fall into that category and therefore does not come within my terms of reference as a folk song collector.
This isn't to say that we don't record songs from revival singers - we do/did - at events based on traditional singing, such as The Willie Clancy Summer School, Forkhill and Ballyliffin.
I know the late Tom Munnelly's collection of 20,000 songs includes numerous self-penned revival singer compositions, but these would be made in similar circumstances to those I have described. If we were writing or talking about our collection, as we occasionally do, we would make a clear distiction between revival and traditional material - as far as we are concerned they come from a different stable and have a different (not better or worse) pedigree and significance.
Wearing a different hat altogether, my personal interest in the folk song revival has led me to gather in recordings from revival singers - but that's something else entirely.
There is a great deal to be said (not here) of the locally made songs we have recorded (in the UK and in Ireland) some of which have become traditional, while others haven't, but not here.
Just to make a point on the whole revival/tradition thing; in my opinion, one of the greatest contributions made to our access to and understanding of our song tradition over the last 30-40 years has been the Roud Index, and much of the importance of that is down to Steve's decision (and ability) to distinguish between revival and tradition.
There is, I believe, a great need for a study of new writings, as distinct from the older songs sung in the revival (and all too often passed off as folk), but that is up to those who are interested in the subject, for me, life is too short as it is.
Jim Carroll