Its not so much about appointing a defence secretary who has experience of defence (Liam Fox does have at least a little) - its got everything to do with listening to those with the experience, rather than publically suggesting that you know better, in the face of all the evidence!
Liam Fox appears to have been pushed very much to the back for some of his previous criticism of policy, as it seems have the service heads. So if those supposidly in senior defence appointments aren't being listened to, then who is? Who will be on the defence board?