Some more light on the "why" of Batman fighting Superman
"So why are Batman and Superman fighting? Entertainment Weekly says that Batman is worried that Superman’s unequaled power makes him more of a potential fascistic overlord than the hero we need, he makes it his duty to take him out of the sky for good."
Interesting take, that seems consistent with the universe they are creating. The Superman they have created is powerful enough to win, but hesitant enough to lose. Things are taking shape, though it still has tremendous fail potential.