A spark may have started the wildfire, but nobody went around lighting each individual tree. That's where the anger comes from, in part. It comes from the helplessness of these situations. The gut-punch reminder that we have no power, no control over the world around us.
When the angel of the Lord appeared to Gideon and told him "The Lord is with you, mighty man of valor," Gideon's response was somewhat valid. "If the Lord is with us, why then has all this happened to us?"