ich - // "What is 'pathetic' - that Mr Corbyn has no particular opinion to offer because he has not personal experience of discussing Mr Zelensky's views with him? "
Yes, in a word. //
I would consider the possibility that Mr Corbyn's comment was taken out of context, and may not have been the sum total of what he said.
This is a common journalistic tool, to make someone appear to say, or not say something, in a way that makes them look bad.
In this instance, Mr Corbyn may have said, when asked about Mr Zelensky, "I have never met him." which he then followed with a twenty-minute monologue detailing his views on Mr Zelensky's situation and that of the wider situation in Ukraine, which of course was not mentioned, in favour of simply cherry-picking one sentence to make Mr Corbyn appear shallow and ignorant to the readers.