In the finale of the second series of BBCs Sherlock, the eponymous character has the following exchange with Jim Moriarty, his arch enemy:
JM: You think you can make me stop the order ? You think you can make me do that? SH: Yes, so do you. JM: Sherlock, your big brother and all the Kings horses couldnt make me do a thing I didnt want to. SH: Yes, but Im not my brother, remember? I am you. Prepared to do anything. Prepared to burn. Prepared to do what ordinary people wont do. You want me to shake hands with you in hell? I wont disappoint you. JM: Nah - you talk big. Nah... youre ordinary. Youre ordinary - youre on the side of the angels. SH: Oh, I may be on the side of the angels... but dont think for one second that I am one.
In his most recent book, I Wear the Black Hat: Grappling With Villains (Real and Imagined), Chuck Klosterman defines a villain as the person who knows the most but cares the least. In the episode A Scandal in Belgravia, Sherlock is told by his aforementioned brother Mycroft that caring is not an advantage. When talking to his companion John Watson in the same episode:
JW: There are lives at stake, Sherlock! Actual human lives - just so I know, do you care about any of them at all? SH: Will caring about them help save them? JW: Nope! SH: Then Ill continue to not make that mistake.
It becomes clear that either A) Sherlock truly does not care about the victims in his cases or B) Sherlock really wants people to believe he does not care about the victims in his cases. Again, in Scandal, Mycroft and John discussing Sherlock:
MH: My brother has the brain of a scientist or a philosopher, yet he elects to be a detective. What might we be able to deduce about his heart? JW: I dont know. MH: Neither do I. But initially, he wanted to be a pirate.
What Mycroft says is very interesting here. On the one hand, he implies that Sherlocks decision to fight on the side of the angels demonstrates that there is an inherent goodness within, that Sherlock in fact does care about the people he helps. Yet, he says that Sherlock wanted to be a pirate as a child, a criminal. Throughout the run of the show, Sherlock presents himself as cold, calculating, and unconcerned with the opinions of others. Despite that, he also has an obsession with proving how clever he is. In The Reichenbach Fall (the second series finale mentioned above), Sherlock says he doesnt care what people think. John responds: Youd care if they thought you were stupid or wrong. Sherlock continues his denial, insisting that he is both brilliant and uncaring. A villain.
In The Hounds of Baskerville, Sherlock describes himself as a show-off. This flies in the face of his assertion that he doesnt care what people think. Why else show off unless to court the praise of others? Sherlock is extremely vain, his designer clothing and propensity for flipping up his coat collar attest to this; its no coincidence that his best friend also happens to blog about his brilliance. When Sherlock explains he does not care about the victims he saves, we know he is telling the truth because its obvious what he really cares about is showing off. He enjoys being three steps ahead of Londons Finest; he enjoys surprising people with his deductions; he enjoys knowing the most and caring the least. Its actually Sherlocks love of bragging that keeps him on the side of the angels. Criminal masterminds like Jim Moriarty must live in secret. When he is put on trial, Moriarty blackmails the jury into finding him innocent; in the eyes of the world he is not a genius spider at the center of a criminal web, as Sherlock describes him. The outcome of the trial makes him into a normal, ordinary man. We know that Moriarty has contempt for ordinary people (as shown in his conversation with Sherlock above), but he has to appear ordinary to the general public in order to continue his work. Sherlock could never handle that; he needs people to know how smart he is. If it was possible to be a kingpin of crime while also bragging about it, Sherlock would depose Moriarty and take over the whole empire (and run it more successfully!), but in the modern world that cant happen. Pirates, or at least our perception of them, in the classic sense, were able to pillage and be famous for it. But now, pirates dont fly a black flag - they get taken out by Navy SEALs. Sherlocks black flag is his overcoat and as long as hes on the side of the angels, he can be as villainous as he wants.