Okay I’m sorry this is hastily thrown together in Paint but seriously can we talk about these two lines.
I love how in the beginning Stark has no respect for Agent Coulson, dislikes everything he’s working for and with and just wants him gone. He won’t even acknowledge Phil as an entity outside of SHIELD; to him, Phil is the annoying messenger, a nameless lapdog that exists to pester him. And then, after what happens, it actually rattles him. For the first time in the movie, he’s shocked and not mouthing off at somebody. And it’s not just him, either - all of the Avengers up until that point are at odds with each other. There they all are, highly skilled or superpowered up, and what are they doing? Bickering. The guy who actually stands up, fights and takes the hit is just that: a guy. Phil, no superpowers, no back up, and a weapon that he doesn’t even know what it does, goes up against a deity with every odd stacked against him because he’s going to do the right thing no matter what. And he pays for it. Loki gets away and the Avengers are separated, but they come back united. The “push”, as Fury worded it. And suddenly Stark not only has respect for Coulson, but he makes a point of letting Loki know very clearly that what he did to Phil - Phil, not Agent; the joking is over - was a big, big, BIG mistake.
If you ask me, they’re not avenging Earth. They’re avenging Phil.