@jj1968
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.
She made claims about other groups he thinks are Nazis based on the original tweet. Given that the first tweet is ambiguous, the idea you can then ascribe opinions to him he has never voiced based purely on speculation is arguably defamatory. Can't see it ever getting to court though, especially if the tweets have been removed and he probably should take a break and have a lie down.
She absolutely didn't, and the tweets are still there.
She retweeted his original tweet, stating "As always a man tells us there are more important things to deal with than women's rights.
Women talking about sex discrimination, proposed legislative overhaul which will remove their rights are Nazis?"
She then tweeted a list of people who have been no-platformed by Universities in the last year or so, to make the point that these people (mostly left-wing women) must be, by Omid's standards, nazis.
A lot of people then went directly to Omid's timeline to tell him he was wrong, and he blamed DrEM for that and ended up with his undies in a bunch because more people on his timeline disagreed with his ill-thought-out and unfunny "joke" than supported it.
IANAL but I don't see any defamation there, just a butt-hurt bloke who, instead of thinking "shit, I might have got this one wrong" decided to double down and blame his shame on a woman with less than 1/5 of his twitter following.
He's an arse.