I dont think his lack of gigs towards the end of his life had anything to do with organisers politics, or with other performers political opinions.
in my experience,the political views of folk club organisers are quite unpredictable and idiosyncratric.
I think the folk club scene at that period,from my recollection [1988 1990], was veering towards a middle of the road, entertainment guitar orientated sound, in fact I would go further and say that even today concertina is favoured unfavourably, compared to guitar.
organisers quite often think nothing of having three or four guitarist singers, in a short space of time, but would never have the same attitude to singer concertinists.
Peter was something unusual,conservative[not in the political sense] folk club organisers [imo] thought he was too much of a financial gamble/ risk to book.