OH MAN YOU ASKED THE RIGHT QUESTION.
And you totally pinpointed it: this is largely predicated on that nasty word ‘addiction.’
If you buy into my reading of Sherlock and John’s relationship as a kind of BDSM power game, then the big issue here is consent. Because consent can often be the only dividing line between abuse and BDSM. If a person asks for it (really asks for it, not in the “she was wearing a short skirt” kind of sense), then it is not abuse.
(And in fact “You asked for it!” is a common justification for abuse and violence, both physical and emotional.)
Consent requires two things: for the consenter to have possession of their faculties, and to have a sufficiently full understanding of what they’re consenting to.
In the very first episode, John is invited by Sherlock (“Could be dangerous”) and warned by Mycroft (“When you walk with Sherlock Holmes, you see the battlefield”). John is in possession of the information and he makes his decision to go with Sherlock anyway.
In The Great Game, he sees past the gloss of Sherlock’s awesomeness and Sherlock fails to give him information that led to John being strapped into a bomb vest. And yet, with one glance, Sherlock queries John’s consent, and John gives it.
(Spoilers down in there somewhere.)
[[MORE]]
Now, in BDSM, sometimes consent itself can be the game—and this can get tricky. It’s one of the reasons why people normally use safewords, so they can preserve the fantasy while still being able to communicate the reality.
And if we read Sherlock and John’s case-solving relationship as BDSM, then we can read them as playing this game. Sherlock doesn’t always tell John things. Sometimes he keeps him in the dark. John typically takes this as a sign that Sherlock knows what’s going on (and therefore has control of the situation) but simply isn’t telling him so that John can feel the fullness of the fear and thrill.
If that’s the case, then it’s critical that John has complete faith in Sherlock, and it also makes total sense that he does. That total faith that Sherlock has or will inevitably gain control of the situation stands in, in this case, for John’s full knowledge of the situation. He consents, with the understanding that even if he doesn’t know what’s going on, Sherlock has it covered.
(Also worth noting: as far as John knows, Sherlock’s never let him down. Though the Fall was a rough patch.)
So far, so good. Now, this paradigm might do interesting things to ASiB (and why Moffat chose to make Irene a dominatrix), and what was going on between Sherlock and John in that episode, which I think a lot of us have always found a tad off-kilter. But especially worth noting in this light is the end of Hounds. Sherlock has drugged John and run him through a terrifying rat maze. It turns out that (as is their agreement) he had full control the whole time. Whoops! Except that he didn’t. As John says, “You got it wrong. It wasn’t in the sugar, you got it wrong.”
Sherlock let John down because if he didn’t understand the situation clearly, then he inevitably didn’t have full control, and the reason it all went okay anyway was pure luck. ”Won’t happen again,” Sherlock tells him.
It also makes more sense of The Empty Hearse. John is upset on the very understandable grounds that Sherlock fucked him over and lied to him, and it wasn’t the kind of game they’d played before. Maybe Sherlock, so very talented at missing the things that are in front of his face, wasn’t even really thinking about the fact that TWO YEARS goes waaaay beyond any kind of reasonable time frame for any kind of game. But by the end, their old contract is back in place. John may be catastrophically pissed off at Sherlock, but he still believes in him, and he proves it by accompanying him on a mission to find a terrorist bomb. And then, in a rigged-up carriage car, Sherlock corners John and terrifies him out of his gourd, and then proves that he had the situation under control all along.
And John offers his forgiveness, but more importantly he laughs and, unspoken but clear, indicates that yes, he’s back in this.
So from the way everything looks, it’s not abuse at all.
But everything changes with His Last Vow, when with a single word Sherlock reframes their relationship. He first implies that John is an addict (“In a way”) and then later baldly states it.
But if John is an addict, then suddenly the question of consent looms huge. If John is an addict, can he be said to have full possession of his faculties? If John is an addict, then all those times when Sherlock has waved ‘danger’ under his nose—were those invitation/warnings, or were those the temptations of a pusher?
If John is an addict, then does he stay at Sherlock’s side because he wants to, or because he needs to?
If John is an addict, then this is all a very bad scene.
But there’s still a question: is John really an addict?
Honestly? I can read this 50/50 either way. And Sherlock himself gives us two possibilities. ”You are addicted to a certain lifestyle. You’re abnormally attracted to dangerous situations and people.” So which is it? An addiction, or an attraction?
I just…there’s a huge knot here, lurking under the surface. So many things could be going on here. Adrenaline addiction, coping mechanisms rampaging out of control, possible factors from John’s background playing a role, plain old personality traits. Could it be an actual physical dependency on adrenaline? Actually I’m not sure, go Google it yourself. Could it be a behavioral addiction? Certainly. Could it be a behavioral pattern/coping mechanism he’s been using at least since the war (PTSD maybe)? Sure. Or maybe John just gets bored easily, and this is his personal fun thing to do. Or maybe for a man who’s gone through so much crap in life, it’s even therapeutic and life-affirming to put his life on the line to save others, and to share that with another person he cares for very much.
And then finally that brings us to the confrontation between John, Sherlock and Mary. In which Sherlock is being 100% honest to John about John’s own desires, needs and tendencies, and yet in the same breath he’s couching everything in terms that liken Sherlock and Mary as being of the same kind, and frames John as having already chosen them (implying it’d be hypocritical to change his mind now).
So is Sherlock being manipulative here? Or just honest? If he’s being manipulative, does he REALIZE he’s being manipulative?
Mary certainly does, from the way she jumps on the phrasing Sherlock uses. Though of course she’s got some pretty urgent reasons to want to persuade John to see her in a sympathetic, desirable light, so I’ll give her a point for being desperate.
And I’m inclined to give Sherlock the point, too. Because even if he frames himself and Mary both as being the same type (dangerous, amoral), he also in the end pushes John back from an emotional place. He forces John back all but physically (“Your way, Sherlock, always your way”) and makes him take up the most unemotional and objective relationship that John could, at this point, possibly have to Mary: she is their client.
And then that’s where we leave John for the next two or three months while he ruminates on this decision.
(Of course we have no idea what goes on in that time. How much he sees of Mary, how much he sees of Sherlock, whether either of them work to persuade him, or what. If you have opinions on what went on there, then that’s likely to color your conclusions about his decision and their relationship to one another.)
So. I don’t think Mary is abusive. The only time Mary actively acts against John is in that room when she’s desperate for John not to leave her entirely. She also very selfishly shoots Sherlock, but that is not an attempt to work against or hurt John, either. Her lies and secrets are not meant to hurt or manipulate John (although they do), but rather simply to avoid rocking the boat and threatening their relationship. She absolutely is selfish, and in shooting Sherlock she chooses her fear of the consequences of her lies over John’s happiness and emotional well-being. But that’s not abuse, that’s just being a bad person.
Sherlock and John, though, is a more complicated question, and one that ultimately I think has to be up to the viewer.
My personal interpretation, if you want it (of course you do, who wouldn’t? ;P), is that mostly what’s between them is consensual, but that now and then Sherlock veers into abusive territory. I think that it is never his intent to be abusive of John, but I also think that when he really wants something, he’ll use the tools at his disposal to get it, and that it is only a very recent development in his life to think of another person before or even at the same time as himself.
And I think that John recognizes and appreciates all that, is generally prepared to work with him, and understands that, to a greater or lesser extent, Sherlock will always be a self-absorbed ass. I think that John does have his limits and is prepared to put his foot down when necessary for his own sake or others, but also that sometimes, he finds that Sherlock being an ass can be a very rousing and entertaining thing.