Danzo is a douche. Because of him many innocent Uchiha (non Coup d'état supporters) died, Shisui was killed, and Itachi and Sasuke's lives were ruined.
I'm also disappointed in Hiruzen. Thousands of people died because he didn't eliminate Danzo. Hiruzen also always talked about peaceful approaches but he never backed up his words with action. He could have talked to the Uchiha personally and tried to reach an agreement.
Fugaku didn't know what was best for his clan by putting them against all of Konoha. Trying to overthrow the Konoha government meant fighting against Root, the regular military, ANBU, citizens, and the Hokage himself. It was a suicide mission.
There were a lot of cowards on both sides not doing what was necessary to reach an agreement.