this probably seems like stating the absolutely obvious but here goes:

someone says: 'antisemitism in the Labour Party was real *but* was exaggerated by the media - which regularly reported an 'existential threat', Simon Heffer said on LBC Corbyn wanted to 'reopen Auschwitz', etc - and that's unacceptable, what does this actually mean for Starmer?

what it means, seen logically, is basically this. 'I do not think it is exaggerated that the man I served under and campaigned to make Prime Minister was an existential threat to British Jews, was planning pogroms, and that Jews were right to want to flee the country'

ie: there's no way of squaring this that doesn't make it clear that this is him lying his fucking head off