If Danzo didn't push for the final solution, the Uchiha would of caused greater damage to Konoha. By the end of it, who knows how many innocents would of been drawn into it?
>Konoha Shinobi
>Civilians
>And the Uchiha clan still
^ All who would of died. People trying to defend their home and those just caught in it. Maybe some of the Uchiha children would of been left alive, and the elderly too. Maybe. The Uchiha were too set on their goal. It would of weakened Konoha in a time of political instability, just a year or two past when the Raikage's blamed Konoha for the death of their ambassador and the Hyuga crisis, and still just out of the last war. Not to mention those who died in the Kyuubi's attack. Konoha could literally not afford this.
What Danzo didn't wasn't morally good. It was the best response in a tense situation.