It would need to be personal and self-critical. On the mural, he would need to admit that he looked at a nakedly antisemitic image and could not see the racism. That his response to hearing it was coming down was to ask, "Why?"
He would need to admit that he was an active member of three separate Facebook groups drenched in anti-Jewish imagery and themes and yet said nothing. He would need to explain how, to quote a colleague, he stood knee-deep in a sewer and somehow didn't notice the stink.
He would need to admit that, for some reason, he has repeatedly stood with or defended antisemites, including Holocaust deniers and 9/11 conspiracy theorists shunned by the wider left (Some details on the Sizer and Eisen cases here) thejc.com/comment/column…
That, for example, Len McCluskey was wrong to dismiss complaints of antisemitism as “mood music” - and that others are wrong to suggest now that Jews are making this stuff up, or exaggerating it or “weaponising” it to damage him.
Such a speech would be very hard for any politician to give. It would require soul-searching and honesty. But his supporters insist he is a truly extraordinary, almost saintly man. So maybe he is capable of it (ends)