I see no evidence to back up,his most Important claims

The bibliography is where the evidence is and it's 1/3 of the book. The main text is his summary of the evidence. As I see it, following this thread, you have come to the book with a closed mind and it has challenged your preconceived ideas and you don't like it. You were criticising Steve Roud early in this thread for not stepping outside the boundaries he had himself imposed, at the same time admitting you hadn't read the whole book, just the bits you were "most interested in". A clear sign you approached with a closed mind.

I am not a folk song scholar just someone who enjoys singing folk songs and has an interest in where the songs came from. However I did spend most of my working life in an academic institution and am well aware of the conventions of scholarly writing and Steve Roud's book follows those conventions, albeit written in a style aimed at a wider audience than the usual academic publications. At the end he suggests where there are major gaps in our knowledge and suggests further lines of research. He also gives a perfectly plausible reason for not including extensive examples of individual songs. He has previously published a book of songs - The New Penguin Book - where you could look if need be, though I suspect you don't actually need to knowing enough songs anyway. I think that criticism is simply something else to beat Steve Roud over the head with.

There have been some interestings ideas in this thread generated by Steve Roud's book but they've largely been drowned out by two people arguing from entrenched positions and neither willing to budge or to give some serious consideration to the points made in the book.

Personally, I found the book interesting and I found the main thrust of his argument convincing. There is so much we don't know and probably never will know but it's important to keep an open mind on the subject and I'm sure in the future more information will come to light. As to the songs themselves, I like Martin Carthy's view on them that the worst thing you can do with them is not to sing them.