McEvedy & Beard had already spread their crypto-ablest propaganda by 1970,
I cannot speak for Charles Shepherd, but McEvedy and Beard had not "already spread their crypto-ablest propaganda by 1970".
Their paper was published in 1970, but they did not represent the basic view of ME within the scientific community, or even within psychiatry. Chief psychiatric textbooks in the 80's either do not mention ME in their volume on neuroses, or place ME in a physical disease section alongside e.g. neurosyphilis, mentioning that McEvedy and Beard suggested hysteria, but this is set against the features of the outbreak suggesting an organic basis, calling it an unsettled argument. And this is psychiatry.
The fact that the psychiatrists who appropriated ME later made extensive use of the McE&B paper for their own ends should not be confused with the notion that theirs was the widely accepted and dominant view at the time.
The researchers studying ME had actually considered hysteria (from the top of my head in the 60s) and discarded it and spoke out against it, then and later, because it did not fit what they observed and found. For example, a report on a symposium on ME at the Royal Society of Medicine in 1978 says: "Some authors have attempted to dismiss this disease as
hysterical (McE&B reference, again), but the evidence now makes such a tenet unacceptable."
The 70's and 80s actually were a time of lively expanding knowledge of ME, exploring issues that look familiar today: issues with metabolism in the cell, very low lymphocyte oxygen uptake, mitochondrial dysfunction, persistent infection, immunological dysfunction, deformed red bood cells, lactic acidosis, impaired capacity to synthesize muscle protein, and more. (And that's with the technical possibilities of that time, which has since improved.)
There was a lot of interesting and important research going on; in a private conversation, a ME patient described the 80s to me as a "hopeful, exciting time" because of that.
I have no problem believing that it occured that individual physicians discarded individual ME patients as hysterical. (It was new, medical misogyny has a long history, and medicine was still male dominated while ME patients were predominantly female.)
But it is a mistake to portray the time up to the early 90s as a period where the view that ME was hysteria was the commonly accepted and dominant one.
It's a topic that I have yet to explore further (I'm currently using my limited energytime to process the topics I have already researched), but other corroborating clues are the fact that in private conversation another ME patient told me they had a GP at the time willing to try out treatments based on contemporary ME science, and a survey (done in the 80s or early 90s) among Scottish GP's that showed that 10% denied the existence of ME - in 1992 this survey was discussed regarding the issue that it could occur that rural patients, with only one GP practise in their community, would have a problem if they had the poor fortune to have that GP practise be one where the GP did not recognise ME - it described a situation where a patient registered with a GP practise in another town using a false address.
Based on what I know I have no issue with the description in the MEActionUK's response.