Speak to BBC frontline staff
"Indeed, a lot of the BBC's content is damn good - something it suggests it couldn't achieve in the market."
The proof? Well the proof is in your next line where you point out "that most of its best content sells well globally and also tends to dominate DVD sales charts in the UK". The BBC consistently beats the crap out of its commercial rivals in quality and innovative programming. We've seen ITV destroy itself by merging over and over into a single behemoth - each time pleading that it would lead to better programmes - and each time a shocking, colossal failure. All that emerged was additional layers of profit-focused managers, and a miserable tide of 'I'm a Pop Celebrity Idol Knight Get Me On X Factor' tripe.
When a company is that big it can't afford to take risks. That's why US TV schedules are full of 2-hour blocks of the same cash cow programmes with the exception of the holy 'sweeps'.
What keeps the BBC innovative is the fact that it can afford to make programmes that don't turn a profit. Thompson's doing his best to undermine and destroy that, but that core idea is exactly what keeps the BBC going... and more importantly keeps a fire under everyone else.