I've read a few times on this thread that the chance of deliberate pilot crash is 'minuscule' or 'x is a thousand times more likley'.
I don't think that's correct. I count 72 fatal crashes in the past 20 years (let's just use this as an approximate number as my counting was done quickly).
How many deliberate episodes of a pilot or first officer steering an aircraft into terrain have occurred over this time period?
This one, Egyptair 990, silk air, air Maroc and probably a few more (many would add MH370 in here - possible, but I'll reserve my judgement until we have the CVR). I think 7 or 8 is the quoted number of commercial jet flights ending in this manner, even if we accept that a couple may be debatable it's still somewhere in the order of 5% plus of fatal crashes being caused by this aetiology.
Therefore, this is not a black swan event. It's a manifest risk that needs to be considered and ameliorated if we're trying to make air travel safer.