IMHO, it's hard to come up with a litmus test because both sides of the debate kinda like the standard motte-and-bailey structure of "criticisms of Israel". In fact, not only are the arguments often motte-and-baileys, there's often a
super-bailey, a bailey for the bailey that basically invokes some kind of "I win either way" gotcha. For example:
Motte: Israel's use of Palestinian "guest workers" who have no opportunity to participate in either a robust Palestinian economy or a neighboring Arab economy, even when those workers receive the Israeli minimum wage or higher, does fit into an analogy to the treatment of black South Africans under apartheid as captive cheap labor. If Israel wants to avoid being subjected to this analogy, it should simply stop exploiting Palestinian labor this way.
Bailey: Israel is an apartheid state, and not exploiting Palestinian labor would just be covering it up. The only way for Israel to stop being an apartheid state is to stop being Jewish-Israeli: dissolve itself into a single state of Palestine ruled by its natural Arab majority.
Super-bailey: Israel is so apartheid, white-supremacist, and settler-colonial that not exploiting Palestinian labor, were it possible or even implemented at some point in existing history, would only make it more racist (see: https://www.jacobinmag.com/2016/10/kibbutz-labor-zionism-ber...). Israel owes these jobs to the Palestinians, as a precursor to the genocide reparations it will pay when it dissolves itself into a single state of Palestine ruled by its natural Arab majority.
So yeah. The people who could just lay down the motte as a serious moral charge don't want to. They want the bailey, or preferably the super-bailey. Likewise, the people who could just admit to the motte and fix the problem are assured that, were they to actually do so, the goalposts would only be moved to the bailey. Then the bailey will be moved to the super-bailey.
