I assume it goes back to the Minsky incident. From what I understand, a trafficked woman/girl at Epstein's island was instructed to sleep with Minsky. Whether or not this was actually carried out is unclear. RMS said to give him the benefit of the doubt, that he likely wouldn't have known that she was being trafficked.
Just another RMS hot take. It was stupid, like a lot of his statements. Not worth canning him IMO.