Although I bow to no-one in my contempt for Mr Corbyn and his increasing inability to inhabit Planet Earth with the rest of us, I feel I must come to his defence on this issue.
Sir Keir said this about Mr Corbyn's position -
'"I've also made it clear that our position in the Labour Party is not to accept the false equivalence between Russian aggression and the acts of Nato."
Which is all very well, but that's not what Mr Corbyn said.
He said, quote -
""I don't blame Nato for the fact that Russia has invaded Ukraine. What I say is look at the thing historically, and look at the process that could happen at the end of the Ukraine war."
That's pretty clear as I read it - Mr Corbyn is categorically not blaming Nato for the situation in Ukraine, and furthermore, he is advocating the potential disbanding of Nato to be discussed when the Ukrainian conflict is concluded, whenever that may be.
Therefore, although I normally scoff along with majority at Mr Corbyn's frankly barmy assessments of what is going on in the world, on this occasion, although I don't agree with his views on Nato, I do think it is unfair for Sir Keir to castigate him for something which he has clearly not said.