the kindest thing the doctor ever did for martha jones was spare her feeling at the end of 'the family of blood'. most of series 3 is characterised by the doctor's disregard for them and insensitivity, but here, right here, he puts them first. i'll try to ignore him ignoring them seconds before by attempting to get joan to join them. martha tells john smith that she loves the doctor. he is everything to her. and that she really hopes the doctor wouldn't remember her confession. so after this, she tries to do damage control, pretending it wasn't a big deal and that she would have said anything to get him to change back.
martha jones is in love with the doctor and wishes he would figure that out for himself, look at her, really look at her and see. but she's clearly not ready to tell him herself.
the doctor clearly does remember what she said. when martha tries to minimise it all, the doctor doesn't stare in confusion and ask what she's talking about. he remembers, but not just that, knows she's telling the truth. this is also why i think it's inexcusable that he goes back to being rude to her and her feelings in the next couple of episodes.
so the doctor does the nicest thing he's ever done and actually considers her feelings, which right now, is embarrassment. she's visibly self conscious and a bit awkward. she wants him to forget it ever happened. so, he goes along with it. for her sake. he sees her feelings plainly and adjusts accordingly for her. it doesn't happen often in this season, but he does it here.
in a more positive spin on the joan scene previously, maybe this scene was a much needed buffer as well as just a 'wrapping up plot points' moment. the doctor is very dismissive to joan's devastation and borders on complete apathy when he essentially rubs it in her face that the man she fell in love with looks exactly like the doctor and is apparently miles better than john. joan brings back him down to earth with her rejection though, so i'd argue that it is this reality check that makes him able to react to martha correctly.
because imagine if the doctor brought the energy he had with joan moments ago to martha. he wouldn't have been anywhere near as considerate. maybe an even darker take is that this entire situation was an excuse for the doctor to go on an ego trip. he could have dealt with the family before but chose not to because he 'was being kind.' maybe this is his way of exacting some vengeance on the universe for his badly dealt hand. the anger at the time war hasn't gone quite yet. his dealing with the family is swift and brutal. and maybe the reason he is so detached to joan's emotions is because he's still moving off the high of essentially acting like a god towards the family, sending them all to hell. maybe when he is strolling away from the son of mine bainescrow, he's walking directly to the cottage where joan is in. maybe this is why he is so insensitive.
