Yes. With anything like this it's a trade off between stopping it and generating more coverage for it. It absolutely is potentiall libellous, but as such no newspaper is going to go near it. The moment City issue any kind of cease and desist/retraction order, that becomes reportable, thus highlighting the accusation to a far wider audience than a few Twitter users.
It's usually only when something really goes mainstream it's worth it, which doesn't alter the cretinous stupidity of the writer for not realising he can be sued for it.
That’s what I was getting at you put it far better than me.