She went a bit further than that, and he didn't say feminists are Nazis, that implication was just assumed by the people attacking him. I think if DrEm's removed the tweet, I can't tell because she's gone private, then it's petty to pursue it and it won't get very far, but if she digs her heels in then he could well have a case
I don't know who Dr Em (M?) is or what she said. I don't think he called Selina Todd a Nazi although I can see how it could be interpreted as that.
He did call the Finnish lady tweeting as @Tarunperin "Adolph" and "Eva Braun" . I don't see how that can be interpreted as anything other than calling her a Nazi. I'm not sure how you can jokingly call someone a Nazi.