Why isn’t Lord McAlpine suing Twitter?

I understand entirely why Lord McAlpine would wish to sue individuals such as George Monbiot for having wrongly tweeted, or re-tweeted, his name in regard to allegations of child sex abuse. Life is too short and we need to find pleasure where we can, and the whole country has indeed enjoyed watching the Moonbat squirm.

But why is he not suing Twitter itself? It is not Philip Schofield who the peer is suing, but ITV. Surely, likewise, Twitter needs to take some responsibility for its output? If, unlike broadcasters, it has no legal responsibility for what is put out through its witless conduit, then surely there is less of a responsibility on the people who use it, too?

Incidentally, I’m out of the country for a couple of weeks and will be blogging sparsely, for which apologies.