Uchiha have some mental disease (I know it's not, but lets call it that), which is triggered when they lose someone dear to them. Lets look at what the known Uchiha have gone through shall we?
Madara, known to have lost 3+ brothers, since Izuna was the only mentioned one, plus losing countless of comrades during that war period
Itachi, killed his whole clan, for the sake of the village. And he didn't think twice about doing what was best for Sasuke, and the leaf. He was still good.
Sasuke, lost his whole clan at the age of 7. And he was still good by age 12, until he knew he had to get stronger to one day face Itachi. The only reason he truly went bad was when he heard of Itachi's true story. You see, Hebi Sasuke wasn't "bad". He just picked any path which'd lead him to his then goal of killing Itachi. He was against killing innocents, and was completely neutral until then. He only got trained by Oro, nothing more. Sasuke himself thought Oro was a sick bastard, and never thought twice of beating his sick ass.
And Obito? Allllll for some biddie. A bit of cheap *****. The boy was 12, he doesn't know what love is. People think there's more to it, but is there? Even when Madara had Obito locked in that cave, Obito was still good, and never stopped thinking about his comrades. He rushed to their aid when he discovered they were cornered by Mist anbu. He was against Madara's motives, until the day she died. Which was when he turned ape shit, killed people, and decided to carry on Madara's legacy
this character has been called a monster, a demon, all those mean stuff just because he wants his fruit back >:U got beaten up by his son in a sense, rikudo IS the heir of the fruit, don't bullshit me with some human guy... got divided of its power, got sealed into a chibaku tensei and blasted into the heavens to be locked up for thousands of years, that's insane,
