It's probably because they were in the wrong and they did defame them.
You don't seem to understand my position: I don't think the Labour party was or is free of anti-antisemitism, I just think the racism in the Tory party is way worse and focusing on the antisemitism in the Labour party was part a stick to beat Corbyn with and part the fact that no really expects better from the Tories.
I have noted the way you tried to imply that the EHRC report was looking into Corbyn personally, when in fact it's looking at the Labour party generally. Not really doing anything with that information, since you're basically known liar at this point. I just think it's funny how blatant you are.