My perspective for what it's worth - this is only political because Corbyn has made it so.
I watched CDS' interview with interest and it was nothing more than a measured explanation of deterrence theory and what is required for it to work. As the professional head of the Armed Forces that is well within his purview, just as explaining the rationale for 2 aircraft carriers would be in the purview of CNS. At no point was Corbyn mentioned by name. I don't recall Mark Carney being dragged over the coals by the Treasury for comments on the economic implications of a BREXIT and he is in a similar if not even more sensitive position given his ability to influence economic market activity.
However Corbyn's response of playing the man rather than the ball suggests to me that he is intellectually incapable of arguing his point, but would instead attack the individual on the basis of inference rather than fact. A weak response from a politician stuck in the sixth form common room.