If he had said "morally" people might have misinterpreted it as being not legal. 'Morally' is subjective. Some people have commited murders and claim that they were morally justified.
So Novak wanted to make sure that his answer was the he wasn't breaking any rules, that everything he did was above board in an objective sense.
I think the News Sports segment that you're referring to is shocking: it's the usual anti-Novak nuance taht has been around since I've been following Novak, in 2005.
All athletes keep their training and recovery routines secret: they don't want to give any advantages to their adversaries. But the way it was phrased (according to what you posted, I didn't hear it) makes it sound as if Novak should have answered and refused to, typical.
People keep talking about Novak's "sudden" transformation, as if he came from nowhere. He was he #3 player for 4 straight years, and in 2010 he was ranked #2 for half the year (although nobody mentioned that fact, except me on several forums
) Then he made his final push and became the #1. If people were surprised, it's because instead of watching tennis, they just read about it.
As someone following Djokovic since 2005 you'd know about the reputation he gathered for being unfit due to his high profile retirements for "breathing problems" and constant MTO antics in 5 setters.
That's the transformation people talk about.
It could be a psychological transformation as much as anything else. He's grown up a bit, cut out some of the gamesmanship and sorted out some problems that were mostly in his head.