The Juubi may not be evil!
Okay, so we all know that Juubi was one hell of a destroyer and killed people during the sage's era.
So here's my theory on how the Juubi wasn't evil:
here, in the bottom right panel we see Obito saying that the Juubi had very foul chakra.
And here, we see Kurama telling Naruto that the Juubi doesn't have any feelings so it cannot be sensed.
So, I think the Juubi is not evil or was before the sage's time. Remember when Jman said something about the sage's time where the war was more worse than now. Maybe the Juubi got tired and well, furious of all those war and decided to end them all at once but was captured by the Sage.
So, why didn't a God like creature destroy all of the humans if it didn't like them so much before?? Maybe he enjoyed the company of humans before the war started and once the war begun decided to end the human race. It was consumed by hatred thus making its chakra foul and evil.
And right now the Juubi hasn't reached its ultimate and final form. Maybe then, we will come to know what the Juubi really thinks about and why it didn't destroy people before.