Yea he was evil he destroyed the leaf and killed the third hokage
It actually is a very interesting question. We don't typically think of Danzo as being evil. Danzo was misguided and his actions were kind of jerkish, but I don't think he was evil. Danzo was the kind of guy for whom the ends justified the means. He was willing to do bad things now, to achieve good things later. Some people might disagree with me, but that's my interpretation. He ordered the slaughter of the Uchiha to help prevent a larger war (and, to get himself a load of free sharingans). You can't argue that between the slaughter of the Uchiha and the invasion of Konoha by Orochimaru that there was peace and stability.
And we know that Danzo and Orochimaru were working together. Danzo's sharingans and hashirama DNA were either implanted or enhanced by Orochimaru. And we know that Danzo didn't allow Root to help defend Konoha when Orochimaru invaded.
Is it possible that Orochimaru and Danzo were a team? That Orochimaru was still loyal to Danzo, and was working on a secret under-cover mission of illegal medical research, research and infiltration of Akatsuki, and actually helping Konoha through secret means? Is it possible that Danzo and Orochimaru agreed to kill Hiruzen, because Hiruzen was getting old and weak and a new Hokage was needed for the village to remain strong and protected? After Minato died, Hiruzen didn't search for a new hokage, and he was getting older and weaker over time.
We know that Itachi did bad things but was secretly a "good guy" in many ways. He kept track of Akatsuki and reported information about their movements back to Konoha. He also prevented Akatsuki from attacking Konoha directly until after his death. Yeah it sucks that he killed the Uchiha, but he did what he did because he was trying to prevent war and keep the village safe and peaceful. Itachi was ordered to do the massacre by Danzo, and likely stayed at least partially loyal to him over the years. (Tobi said that Itachi was trying to warn Danzo when he came back to the village the first time, but that might have been Tobi lying. Itachi might have still been loyal to Danzo).
Let's put out a theory that secretly Orochimaru was a "good guy" by some definition and was loyal to the village. The plan goes something like this:
1) Orochimaru forms the hidden sound village, kills the Kazekage and forms an alliance with Sunagakure.
2) Orochimaru invades Konoha, with permission from Danzo and kills Hiruzen, the weak old Hokage.
3) Danzo finally leads a defense and ends the invasion. He becomes the new, stronger hokage.
4) Danzo, with his sharingan and Hashirama DNA, is able to take the 1-tail from Gaara, giving two tailed beasts to Konoha.
5) Sunagakure, without it's jinchuuriki and without a Kazekage is extremely weak. That village is forced to either form a permanent military alliance with Konoha or, better yet, surrender unconditionally and become a possession of Konoha.
6) Likewise, with Orochimaru in the lead, The Hidden Sound village becomes a military ally for Konoha. Orochimaru is able to continue "illegal" research there, which can be used to help make Konoha stronger.
If you think about the plan this way, Konoha actually becomes much stronger, gains an extra tailed beast, and removes a potential enemy village from its list of threats. It's actually a kind of good thing, in the long term. With the combined power of three hidden villages, two jinchuurikis and Itachi and Orochimaru on their side, it would have been possible for Konoha to fight Akatsuki itself, and prevent the fourth world war from happening.
I dont' know if any of this is true, but it is very interesting to think about it.