This far out, anything WB puts out would be strictly for the hardcore fans...
I agree, and it's not like the hardcore fans are monolithic sources of adoration either.
Probably 7/10ths of the Force Awakens' extended newscycle was "#crossguardgate" nonsense, which doesn't necessarily do the film any favors. To be clear, I'm not saying anything about the validity of such discussion, I'm saying, I doubt Disney was hoping for most of the discussion about the teaser to be nerdwars over the efficacy of something in 10 frames of the teaser.
Instead, it kinda just paints the hardcore as petty and something to be mocked rather than eagerly joined (see: Colbert addressing it).
You show that to a general audience, they probably don't get as hyped as the hardcore, but they also aren't as so pedantically critical about every little thing... they just generally come away with positive feelings.
Showing stuff super early can garner the endorsement of hardcore fans, which can sway some casuals... but it can also spawn unnecessary pre-judgment and bile from hardcore people who take things too seriously, which can poison some casuals. Early is far from a good or certain gamble.
The main justification, I can imagine, for showing stuff early is to inoculate the audience with stuff so that they get used to it, have that discussion and get it out of their system, before heading into the thing itself. The vast majority of people who watch MOS after seeing all the controversy, don't find it nearly as controversial as the discussion seemed to imply... of course, giving up surprise isn't something most filmmakers want to do.
...which means it'll probably be at Comicon.
That's probably a solid move to the extent that fandom is monolithic, reports out of "Hall H" strongly tend towards the positive. I don't think it's anything so sinister as Stockholm Syndrome, but there's justifiably a certain amount of cognitive dissonance that's going to drive excitement in the Hall... you've paid to be there, you're waited hours upon hours to be there, your expectation is through the roof, you feed off the energy of everyone else there... so you're going to be excited about what you're shown, otherwise all of that was for naught.
If the WB wants to control a consistent positive buzz about BvS, ComiCon is a good place to do it.
