braticus, are you completely unaware of the huge rise in antisemitism in the UK?
The fact that some Jews go on these marches is not the point you think it is. I understand why they are there - they include family and friends of mine - but they are actually not the people who are bearing the brunt. Those are the visible orthodox Jews who are the most attacked.
Second are Jewish students at universities, who are in a very hostile climate exacerbated by these marches. And indeed those of us who work in left of centre workplaces: I know I am keeping my head down.
I don't think the marches should be banned and I don't think most marchers are actively anti semitic. I'm sure I could go and join them and not get any hassle. But what would happen if I went carrying a banner calling out Hamas as well as Netanyahu? What would happen if I challenged people carrying antisemitic banners? Why aren't more of the 'nice' marchers challenging those banners?
I think we all know that the answer is it is far, far easier to go with the flow and pretend not to see, pretend not to hear, act all gobsmacked when Jews complain. "Well, I'm really sorry if you are offended, but I think you'll find that's a You problem".