Understanding someone's actions doesn't mean I would agree with them. We saw Obito's transformation and know why he did the things he did. I understand Obito's character, that doesn't mean I accept what he did was right.
Rapists and murderers probably think what they're doing is right. So does that mean if I understood them, I would agree with them? Not at all.
The standard of living is made by the community, not the individual, and that standard changes through time. But there are some things that remained present throughout history.
Killing, rape, lying, stealing, etc. are considered acts of evil by almost everyone on the planet in any point in history.
The entire NV disagreed with Obito, including Obito himself. So yes, what he did was wrong.