1/ I find myself flip-flopping on the point that @mehdirhasan makes here. My reading of the IHRA definition is that it includes Israel because, objectively, Israel is a central part of most Jews' identity. So whereas those who feel strongly about Israel-Palestine would prefer...
2/ ... to separate Israel and Jewishness so they never meet, the reality is that Jews experience prejudice which involves Israel. For example, comparing Israel and Nazis (when using the comparison to grossly inflate the actions of Israelis, or underplay the Holocaust), or...
3/ ... saying Jews have a loyalty to Israel or Zionism which makes them disloyal to their 'host' countries. Or calling for all Jews to be removed from Israel, i.e. ethnic cleansing. I too would prefer for Israel to be taken out of antisemtism but it is unrealistic.
4/ That is why IHRA example include references to Israel. It's clearly not an attempt to put a stop to criticism of Israel, which is why it says that "criticism of Israel similar to that leveled against any other country cannot be regarded as antisemitic" holocaustremembrance.com/working-defini… 
5/ And it's also why the examples are only *examples* with an important proviso "could, taking into account the overall context, include". Ultimately, the IHRA definition leaves it up to decision makers to decide whether something was antisemitic, taking into account the context
6/ What about the example which Labour, apparently, want to exclude? "Denying the Jewish people their right to self-determination, e.g., by claiming that the existence of a State of Israel is a racist endeavor." I agree with Mehdi that this is the most difficult one...
7/ ... and I too am uncomfortable with dredging through Corbyn's previous statements to see if he questioned the right of Israel to exist. But I also think that that with good faith and a decent process, the IHRA examples are sufficiently qualified to allow political speech.
8/ And the difference of accepting the definition in terms of building trust with the Jewish community would be huge. This isn't a debate which is happening in isolation, it is at the tail end of a terrible and terribly handled crisis for the Jewish community and Labour.
9/ Finally, to attempt to answer Mehdi's important point, antisemitism doesn't look like Der Sturmer now, it has moved with the times and Israel often plays a role. To truly reduce antisemitism, it is crucial to build sensitivity to that point. Not easy, not neat, but the reality
