Counter blow
I think this speech is really a response to the recent suggestion of making the Beeb PTV. It's intended to make whoever that was realise it might be better to let things stay as they are.
What Tony Hall really needs to do to justify licensing is to raise programme standards to what they were at in the heyday by assuming that at least a reasonable proportion of viewers and listeners have an attention span that lasts a whole hour. Horizon would be a good litmus test; it was one of their best achievements in terms of quality achieved over a long run and has subsequently fallen furthest.