Something to be said for how the Doctor always has a sense of superiority when it comes to the Master’s perceived insanity. The Doctor is not exactly an example of a stable person, but they repeatedly either don’t believe the Master about the drums and blame it on their insanity, or is downright cruel about it.
In the End of Time, the Doctor admits that he never believed the Master about the drums, and just thought it was their “insanity”, which adds a condescending undertone to all his offers to help up to that point.
In the audio Death Match, the Doctor states “All your plans, your plots, they're just distractions from your own insanity.”, in the same audio he says “Wherever you go, whatever you do, you're still stuck inside that fatuous head of yours, alone with your madness.”
For being their best friend, and having seen the impact their perceived insanity has had on them, and priding themself on kindness, and being partially responsible for the Master’s insanity (as Torvic’s murder was part of it), the Doctor displays an alarming level callousness towards the Master in this aspect of their life. While maintaining the belief that they want to help them, and that they are acting in the Master’s best interest in mind.
