A person of good intelligence and sensitivity cannot exist in this society very long without having some anger about the inequality - and it’s not just a bleeding-heart, knee-jerk, liberal kind of a thing - it is just a normal human reaction to a nonsensical set of values where we have cinnamon flavored dental floss and there are people sleeping in the street.
[He] is drawn like a moth to the flame to Sherlock. And I think what they discover through each other is that they absolutely fit. They need each other. It’s the idea that he’s the grounding anchor to this rather ethereal, otherworldly, slightly bombastic character. He brings him to Earth and also helps him pragmatically.