I don't understand how the Royal Society doesn't realise how much damage it did to their reputation to admit him in the first place.
Even before all of the fascist stuff, he was not a scientist, not a researcher. His contributions to science and engineering were that he was a rich person who funded some work.
Making him a FRS made it very clear that it's not an institution for scientists, it's an institution for plutocrats.
It used to be that being a FRS was something to aspire to an a scientific career. Now it's an easy decline if offered, because who would want to be associated with an institution like that?