Spot on.
The reply you suggested is exactly what he should have said.
He's still got a lot to learn. It's the first time - I think - he has moved between clubs in the same division. He's handled it all very badly. At this level he needs a thicker skin.
It might well have blown over.
In normal circumstances.
However the poaching of Bruno was the game changer ( and I know Bruno gave the final Yes/No on that ). If that hadn't happened the wound of Potter leaving would have been far more superficial.
Instead of taking the "nothing to apologise for" line maybe a better response would be to recognise that football is an emotional game, that feelings can still be raw, talk something about giving it time and after that time, in the cold light of day, hoping that things will be viewed...
There's another thread on this but basically it boils down to :
1 - Borrow £17 million.
2 - Buy Cucurella.
3 - Sell Cucurella for £65 million.
4 - Pay back £17 million.
5 - Sit back and grin when counting the profit.