Netzer, I am pretty sure, is not Jewish. So this another example of non-Jews believing it is their place and prerogative to tell Jews what it means to be a good Jew.
This entitlement is one I am seeing increasingly often in right-wing discourse, and it is not getting nearly enough attention. It is, simply put, a monster lurking beneath the discursive waters about Jews, because it offers a way for non-Jews (typically Christians) to harmonize their abstract claims of being great friends of the Jewish people with their very concrete seething hatred for the actual Jews in America and around the world who do not behave according to their expectations. When they hate those Jews, it is not hatred of Jews; it is the opposite, it is hating those Jews for being bad Jews. In their twisted imagination, the most naked antisemitism becomes almost a form of allyship -- protecting "the Jews" from, you know, actual Jews.
Again, Netzer is not acting in isolation here. This sort of discourse is an emergent pattern, and mark my words, it is going to be a key driver of a new wave of antisemitism (thinly presented as philosemitism) that purports to love Jews even as it intentionally and expressly drives hate towards the vast majority of Jews. And this logic also of course fits in with Christian supersessionism -- the idea that Christians, ultimately, are the true inheritors of Judaism and so have the prerogative to declare what is and is not authentically Jewish. So even when it isn't overtly hateful, it's still inherently antisemitic. But increasingly, that hate and disdain for Jews is wide open.
Non-Jews have no authority to tell Jews what being a good Jew means. If Jews do not behave in manner that coheres to Christian understandings of what it means to be Jewish, that's a them problem, not an us problem. When it comes attached to such an obvious wretch as Netzer, hopefully that's obvious enough. But this is a problem that goes way beyond him, and as far as I can tell a lot of the big antisemitism watchdogs are slow to catch on.*
* I am very proud that the Nexus document on the connection between Israel and antisemitism, which I helped draft, does gesture at this practice in stating that "[d]enigrating or denying the Jewish identity of certain Jews because they are perceived as holding the “wrong” position (whether too critical or too favorable) on Israel" is a form of antisemitism. But that is very much an exception.