1. The Chitarui is an invasion force set to conquer earth. They were not there to kill or obtain the Avengers. There would be no reason to follow the Avengers anywhere. The Avengers did the right thing, considering the World Council decided to drop a bomb on New York City. 2. They were SHIELD buildings and civilian or commercial buildings. "It's all part of the plan" as the Joker put it. Yes, parts of Metropolis was destroyed before Superman arrived, but much more it was destroyed after he got there. I think there was about a good 15 to 20 minutes (or it just felt that way) of Superman and Zod throwing each other through buildings. Having Superman realize his contribution to the damages would change everything. There would be no arguments as it would be self evident that Superman tried to minimize the damage of Metropolis.