Re: "What goes through someone's head when they do that?"
He's a lawyer.
To clarify, I didn't mean to imply that lawyers are inherently untrustworthy, money-obsessed folk. At least no more than anyone else.
What I really meant to imply was that, perhaps, the necessity of putting your personal feelings, scruples and (in some cases) dignity and shame aside in order to do what your client wants enables you to become so desensitised to that compromise that you can reach a point where you stand up - not just before a jury of your peers but an entire country of them - and repeat a party-line that you know to be a false and that has publicly been shown to be false by everyone qualified to know.
That background must also, presumably, admirably condition you to be able to hear a direct, unambiguous question and respond with carefully-worded irrelevancies or to impugn those who question you as misinformed while still, deliberately, refusing to answer.
To be able to do that day in and day out with such ease must take a level of practice that I am glad I have not had the occasion to acquire.