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It seems to me that the question of artistic merit (as subjective as the broader question of taste) is being subordinated to the test of whether the "artist" has been paid or not."
Not by me, it hasn't
I have consistently made the comparison between the superior quality of the songs made for money (under pressure) and the superior quality of the traditional songs
Steve Gardham examples of broadsides from the Holloway and Black collection and his hasty departure seem be an acknowledgement on his part that there is no doubt on that question, but of course, anybody is free to take the point up again
Money in itself is an incidental - but the motivation of payment for making songs most certainly is not

Laycock, and especially Bamford (author of 'Passages in the Life of a Radical') may have put out songs on broadsides, but their compositions were created to illustrate the conditions of the times, that was why the songs were created - money was an addition.
"when we don't know (except in rare cases) who was paid for what and who wasn't or under what circumstances?"
We know that the broadside trade was based on making a profit
"We have no right to airbrush hunting songs even when we disapprove of hunting,"
Nobody is suggesting this Dick
That these songs exited and were sung makes them part of the repertoire
If songs in praise of hanging, drawing and quartering existed, they would be part of the reperoire
THat doesn't mean they have an automatic place in today's repertoire
As far as I know, opposition to hunting is a relatively modern phenomenon anyway and would in no way effect the collecting of such songs.

Many of the collectors and anthologists, the Rev Sabine Baring Gould including, may not have published bawdy and erotic songs, but they kept them in manuscript form (Bishop Percy's 'Loose and Humorous Songs' being a prime example of such)
Occasionally, if you thumb through the Folk Song Journals you will find examples of songs not being documented, such as 'The Girl from Lowestoft (The Hole in the Wall)', but many survived Victorian prudery
Sharp and his crowd aimed to get songs into schools as a way to preserve them; under these circumstances censorship was inevitable
Jim Carroll