The problem with Labour and antisemitism is a wider problem on the left.
Successive Israeli govts have behaved despicably toward the Palestinians and this has reached a nadir under Netanyahu. Calling out the Israeli govt for its many crimes against humanity is to be expected from anyone who is moderately progressive.
The problem is that when decrying Zionism the left too often seem to be ignoring history from the mid twentieth century on. Israel exists, and practically no Israelis or the wider Jewish diaspora wants Israel to disappear. Calling for a democratic secular state, as many do on the far left, is to ignore the world as it is and try to start from some imaginary ideal state.
When folk on the Labour left attack zionism they should be mindful that there are zionists and zionists. Peace Now, a worthy organisation, are zionist but of a very different stripe from Likud
The only viable solution to Israel/Palestine is a genuine two state solution; one which offers a real Palestinian state rather than the dribs and drabs Israel has grudgingly handed over.