Protecting civilians was already a theme in the first Avengers movie, but it’s even more prominent here, perhaps in response to criticism of DC’s Man of Steel on this point.
One can't wonder if this is Joss Whedon giving a big middle finger to Zack Snyder's Man of Steel , which seemed not to care much about puny humans becoming collateral damage as interplanetary gods smashed up the place.
There's a pointed emphasis on avoiding the kind of collateral damage for which Man of Steel 's finale (and for that matter the Avengers Assemble finale) was so heavily criticised, with the team talking up the importance of keeping civilians safe amidst the smash-happy chaos.
What “Age of Ultron” also has is a sense of fun, which persists even when things go kablooey — not always the case with other superhero films (yes, I’m scowling at you, “Man of Steel”).
I have to think this obsessive, specific humanism is in response in part to the disappointed horror levelled against Man of Steel--it's too meticulous, too flagrant, to be accidental.