BPS stands for biopsychosocial, which is not evil in and of itself. In relation to ME/CFS it means that we are sick because of false beliefs and deconditioning. The BPS people say explain ME/CFS thusly: we got mono (or some other random thing) naturally we felt awful for a long while and got very out of shape. When we tried to get in shape again it hurt, and we mistook this couch potato to 5K pain as a sign that we were still sick. Then we got more out of shape because we were afraid of the pain of getting back in shape and gradually worked ourselves into a tizzy of thinking we had a "real illness" instead of merely being out of shape and afraid to exercise our way out of it. In short, we are malingering hypochondriacs, but are too stubborn (or delusional) to admit it.
Some of us have managed to (falsely) convince our family and friends we are sick. They support our delusions and take care of us, merely maintaining our fantasies of illness and supporting us in being out of shape. Children in the UK are sometimes taken from their parents under this delusion. Sometimes the children are very seriously harmed by being forced to exercise themselves back to health.
Properly applied the BPS model acknowledges that an illness has social and pyschological consequences for its sufferers. Improperly applied, as it is to us, it suggests that a person can think themselves sick and that our thoughts and our social milieu interact to keep us sick. When it comes to ME/CFS, the BPS people happily forget about the bio part of the equation and misunderstand the psycho and social aspects. They insist on treating us with psychiatric interventions that are at best useless, and at worst, quite harmful.
See the work of David Tuller at the Virology blog https://www.virology.ws/
for a description of BPS research and the ways he is trying to fight them and protect us.