" I understand one of Jim's arguments to be that, because the broadsides are mostly a dunghill, therefore the excellent songs that were collected can't have started life there "
Much more complicated than that Richard
I've been labouring over an article for nearly a year now, which I have yet to get properly started
We don't know who made folk songs and probably never shall, so in the end it's down to sorting our what we do know and using common sense
The Irish rural and urban working people made local songs in their many thousands, as did the Scots with their output of Bothy Songs, on the spot waulking songs, their political pieces.... and many other examples
The non-literate Travellers, both Irish and Scots, were still making songs right into the 1970s
How likely is it that the English rural working people were alone in these Islands in being almost fully reliant on hack writers for songs about every aspect of daily life - which basically what our folk repertoire is
When I challenged Steve Gardham with this his reply was that the English agricultural workers were 'far to busy earning a living to make songs'
The greatest output of songs in Ireland came from hardship such as forced emigration, mass evictions, land wars,, wars of national independence -
Hardship inspired songwriting, not discouraged it
Our songs are based on working people's vernacular, they contain insider knowledge on work practices and leisure activities, the sympathies of the songs lie invariably with the persecuted and the poor....
A desk-bound hack would have to have possessed the skills and the politico-social leanings of a Steinbeck or a Robert Tressell to have made such socially volatile stuff
Hacks were human conveyor belts churning out their doggerel to stay alive and their largely shoddy compositions show exactly that

And that's just the start
You have the problems of poor and non-existent literacy as a disincentive to learn songs from print, the tendency to treat printed texts as sacrosanct (a regular comment from our singers), which acts against such songs passing into versions.....
Non literate Travellers have been the main carriers of our songs in Ireland and Scotland
There is much, much more on this question that remains unresolved and unanswered

Up to the last decade, Maccoll's statement at the end of the Song Carriers summarised the belief of most folk enthusiasts, from researcher in folk song to broadside experts like Bob Thomson and Leslie Shepherd

"Well, there they are, the songs of our people. Some of them have been centuries in the making, some of them undoubtedly were born on the broadside presses. Some have the marvellous perfection of stones shaped by the sea's movement. Others are as brash as a cup-final crowd. They were made by professional bards and by unknown poets at the plough-stilts and the handloom. They are tender, harsh,, passionate, ironical, simple, profound.... as varied, indeed, as the landscape of this island."

What has changed to make that statement no longer valid ? - nothing, as far as I can see
Jim