....... where exactly do the BMoF actually promote this " nasty folksy Green Man imagery which owes more to The Wicker Man than the wondrous reality of British Folk Custom."?

True they include images of of these celebrations (or one at least) in their extensive range of observation (as displayed here but I can see nothing other than an observation that it exists, which is does, and is thus observable. They don't appear to be expressing a judgement one way or the other. Are you objecting to Doc or them even acknowledging its existence?

I don't actually disagree with you when you express a dislike for 'fantasy folklorism'   but I would reserve the right to observe it and make it available for other people to observe and comment on. It's up to them to make their minds up about it and not up to you or me or Doc or BMoF to filter and sanitise their experience before they consume it. We had enough of that from the early collectors.