The words used were clumsy and might even betray a mindset (in the audience member) that strays onto the wrong side of the line. However, just in common sense usage, in terms of conveying where prominent Labour politicians are getting their money, they certainly have pro-Israeli sponsors (as in, people who donate):
morningstaronline.co.uk
Just moving this on to the 2nd bit highlighted, surely the switching between and deliberate confusion of anti-semitism and criticism of the state of Israel is the problem. We might quibble as to whether Labour is being 'sponsored by' Israel (certainly not directly, though the money Starmer got for his leadership campaign probably fits that definition of 'sponsored') or just from 'pro-Israeli groups'. But the reality is they are receiving funding, supporting mass murder by Israel and have used this in the most cynical fashion to remove the left from the party. It should be unproblematic to say that. You shouldn't have to be on the defensive, awaiting accusations of antisemitism when you say that, accusations that then blunt the criticisms of Israel you are making. Yes, of course, do that without generalisations about Jewish people, without any of the filthy conspiracy theories that slosh around with antisemitism. But equally, call out the way antisemitism is deployed. And Mason is doing exactly that here, flourishing antisemitism as a trump card. And the slaughter continues.