You may know that the Labour Party has 'institutional' anti-semitic problems, but I don't. I haven't seen it from the inside for a while - I left the Labour Party 4 years ago - but I have followed the story very closely. All of the evidence I have seen says that Labour has less of a problem than other main parties, and has done much more to tackle it. The perception is different of course. Perception has its own reality, and the relationship between Labour and parts of the UK Jewish community is now toxic.
There are anti-semites in the Labour Party like in all parties, and there are thousands of racist creeps out there who will abuse and threaten people on social media - including Jewish Labour MPs - but I haven't seen any evidence to convince me that this comes from Jeremy Corbyn or Momentum. The opposite in fact. My problem with Corbyn is weak leadership which means he is backing off his principled position in the face of the PLP and media onslaught, but still getting smeared - the worst of all worlds.
I don't normally do conspiracies. I am convinced that cock ups explain most events. But in this case I am 100% convinced that the whole move to redefine anti-semitism internationally (to conflate it with criticism of Israel) has been pushed by Israel in response to successes of the BDS movement. I am convinced that some of the black and Jewish Labour members who have been expelled (like Wadsworth and Greenstein) are victims of an internal witch hunt. I am also convinced that the charge of anti-semitism has been weaponised to attack Corbyn. You may know Margaret Hodge and her motivations better than me. I know she lost family in the holocaust (as have many on the other side of the argument) and I'm sure she is upset, but she is also one of the leaders of the Get Corbyn campaign who initiated the PLP no confidence vote that sparked the Owen Smith challenge.
But to go back to the OP - whilst Labour tears itself apart with Part X of its civil war, there is no effective opposition in Parliament.