The issue was just too toxic - probably on both sides.
In both NJ and Vermont where I have lived and was a member of a synagogue, there have been many many talks and forums that were all variations on "how to talk about Israel civilly without fracturing the community".
I think October 7 changed that. Immediately, many fearing Israel's predictable reaction did not say silent as Jews and allies mourned the huge loss of life and loss of their feelings of safety.
Then as the attacks on Gaza spun to levels unheard of in any earlier Gaza War, in some areas any criticism of Israel was labeled antisemitic. Part of the problem was a definition that declared a comment antisemitic if it criticized Israel if there were other countries guilty of the same actions not mentioned. As there is significant unambiguous antisemitism, calling most criticism of Israel antisemitic, weakens the word.
Given that the situation in Gaza and the West Bank seems to become more extreme by the day, it hurts that the hateful despicable actions of Hamas may lead Israel to destroy its own democracy.
Mamdani has not himself used the words that Shapiro cautions him on not calling his supporters on. His comment that he supports a Democratic Israel with equal rights for all. Said about any country except Israel, this is standard American values. In addition, American policy under every nonTrump President has been for a two state solution. The norm was being against the West Bank settlements rather than the Trump/Netanyahu vision of moving Palestinians out of most of Gaza and annexing most of the West Bank.
I think that 100% pro Israel support has drastically decreased in recent months. In fact, some articles spoke of Cuomo telling Jewish audiences that they needed to "'talk to their kids" mentioning Mamdani got over half of the Jewish vote.