Agreed. Oh wait... but... but... being "unprofessional" or having "poor boundaries" is a far cry from "sexist". Labels matter... getting them right does too.
Who used the term "sexist"? Not mjg, and the BBC article only mentions it in terms of the ensuing debate. I have no doubt that mjg avoided using it, in part, because people seize upon it to derail the discussion, as you seem to be doing. Guess what - labels don't matter to people who don't feel welcome. They're just going to leave, and while some people don't care, others would like this field to be a bit more welcoming to others, and once again, that's why this matters.