The Doctor wouldn't have expected any other reaction from Sarah Jane, no matter how much he'd tried to rationalize it to her. Though, he was quite certain that had she been here the day of the nudity, those running this place very well might have chosen her as one of their subjects.
'More than capable,' Sarah Jane said, and the Doctor nodded in the affirmative. This could just be another experiment itself - to see how he'd react if something happened to Martha when he was off being careless. It could be. Could be.
"Your son? You have a son?" The Doctor smile turned from quizzical to nearly brimming with happiness. "Oh! What's his name then? Tell me all about him!"