In series 4 episode 1 of the TV series Sherlock, The Six Thatchers, when John, Sherlock and Lestrade are in the Wellsburough's mansion and Sherlock is on a video call with Mary he tells her "All people are stupid... Most people." and then Lestrade says "Bizarre enough though, isn't it, to be him? I mean, it's right up your strasse." adding a slight selfish smile as if he's continuing the joke they had with John about Sherlock being exactly like a baby. Only I don't get it. Can someone explain it to me, please?