I find it bewildering that someone of Michael Marrus's intellect and stature would say that. We all have off days, but still...

As to the petition's requests/demands (the article is vague as to what they are, precisely: "the petition asks" vs "this demand" in sequential paragraphs, and it makes a difference), I would say:
apologise - definitely
mandatory anti-racism training - probably (although I'm never clear as to how that is conducted, what its content, and, ultimately, how effective on a deep level); some might find it irksome, but that's not an argument against, just an invitation to parody all concerned (justifiably or not)
changing the title from Master - fatuous