The Taliban can perhaps be admired for their conviction to their faith and their sense of loyalty to each other.
Clearly, in the storm of protest (including from an MP from the anti-war, anti-army, anti-pretty much everything ilLib Dims accusing him of "giving comfort and succour to the enemy") it was an impolitic thing to do - and, despite his apology (which has itself been attacked), he is going to be pretty much on the defensive for some time and has probably done his reputation permanent (hopefully not terminal) harm.
But was what he said wrong? I don't think that it is clear cut. Yes, some of the Taliban are fighting for money, some are fighting to keep evil crusaders out of the Dar-al-Islam, some just are fighting to keep outsiders* away from their mountain / village / compound / poppy field, etc. However, regardless of the motivation, it is axiomatic that you should not underestimate your enemy and, since before the "Art of War" went beta, that a good commander will try to understand the enemy - capabilities and motivations, strengths and weaknesses. The religious faith or even fervour of the Taliban is an important consideration in understanding them.
And, as I was composing this, Bruce Schneier's monthly Cryptogram brought my attention to this article. It is also axiomatic, particularly amongst retired sergeants, that sergeants run the army. I would disagree slightly - it is the core component of experienced soldiers, many of whom are, indeed, sergeants but some will also be your experienced captains and majors - anyway, different discussion. One of the implications of the report is that the equivalent of the sergeants within the terrorist cells are chosen by the old Soviet system (selected on joining for some combination of brains, political or religious orthodoxy, hereditary or simple nepotism etc) rather than the Western (since the time of the Roman legions) version stressing actual (combat or otherwise) experience. Bodes ill for your ability to learn from your mistakes (even if your successes don't blow you up!)
* Not just Brits, Yanks or even Russians but also those Kabul townies who've never chased a goat around a mountain.