I don't want to say for 100% certain that the osama letter thing is part of this pivot but the timing is sus. My take on that letter is that the antisemitism contained within it could disconnect anti-zionist jews from anti-zionist movements which makes it very dangerous.
We all know already how much antisemitism benefits zionism.
The ADL chose in the aughts to link any critique of Israel with anti-Semitism, and it's becoming more clear how bullshit it is. People learn.
Also, most non-Jewish people who support Israel don't really care about anti-semitism