All agents who call for suicidal measures are at fault.
The left called for suicidal measures [to be effected in Iran in the last days of the Shah].
Therefore the left is at fault, — Jedothek

If this is truly the argument given, then I don't see an undistributed middle. Are you sure you got this part right?

[edit] after having watched the clip from about a minute before your suggested timestamp to the point where he says it, I don't think that it's obvious at all that the logic you laid out here is the thing he's calling an undistributed middle. That being said, I'm not entirely sure what he is calling that.

For those, like me, who didn't know: Fallacy of the undistributed middle

If I can add to yours, a term in a classical syllogism is distributed when somewhere in the syllogism the important quality is said of all the members of that term.
Example:
All men are mortal.
Socrates is a man.
Socrates is mortal.

Three terms, man/men, Socrates, mortal.
All men - men is distributed because something is said about all of them.
"Mortal" is not distributed.
Socrates is distributed, because something is said about all of Socrates - this is a little tricky, but not very tricky.

If man/men were not distributed, then it might read,
Some men are mortal.
Socrates is a man
Socrates is mortal.

And the problem with that conclusion should be clearly evident.

Syllogistic reasoning is not too difficult, although a little strange at first. Worth the effort of learning.

As i suggested, that syllogism was only an attempt on my part to reconstruct Buckley's argument: I suspected it was irrelevant to Hitchens' reply because, as we both said, it contains no undistributed middle.

I would appreciate any conjectures from folks as to what exactly was the argument from Buckley that Hitchens called fallacious.